feat: configurable AI-bridge trigger word for telegram listener

The listener's "ai " bridge prefix was hard-coded. Messages starting
with <prefix> + space (case-insensitive, literal match) are now
forwarded to Gemini; default stays "ai".

- TELEGRAM_AI_PREFIX in telegram.env (default ai), hot-reloaded per
  message like the command map — no daemon restart needed
- New 'prefix' verb: pos communication telegram listener prefix [word]
  (validated [A-Za-z0-9][A-Za-z0-9_-]*; writes telegram.env chmod 600)
- Field added to the telegram # POS_CONFIG: scope (sender header) so
  'pos config telegram' edits it too
- --status shows the current prefix; usage + POS_SUBCMDS: prefix
  (completions regenerated)
- Matching via scoped nocasematch + quoted-literal =~ prefix;
  ai_bridge_prefix() precedence: env file > env var > default ai

Verified: routing harness (default/custom/case-insensitive/reset/
fallback/unknown-command) green, CLI verb tests, dispatch smoke,
pos config render, gates 0 FAIL 0 WARN.

AGENT_TODO.md

@@ -136,3 +136,4 @@ summary (newest last).
 - **2026-08-23** — Menu Phase 2 + firewall style-migration (decision "a" activated: P1 landed, `lib/menu-lib.sh` exists). `pos docker vbox` (157→261): 6-item menu hub over the inline case verbs via a quoted self-invocation `menu_self` (verbs never re-enter the menu → no recursion); `enter` hands over the terminal and returns to the loop; rm/create behind VM-naming y/N. `pos network download` (950→1104): 13-item top-verb map onto existing cmd_* fns — add URL (`menu_ask_value`, optional `--tmux`), gid-pick → info/pause/resume/remove/restart (remove names name+gid before delete), typed-confirm purge, watch handover, daemon start/stop (stop confirmed); non-fatal RPC liveness gate (`-m 3`) keeps queue views alive on a dead daemon; deliberately NOT added to INTERACTIVE_CMDS — menu-lib's tty-guarded reads make membership unnecessary and keep tee-logging for all scripted verbs (survey E-002; Reviewer traced the lint pass as honest through `uses_stdin`). `pos system firewall` (308→325) migrated to repo-standard mechanics ONLY: menu heredoc render → stderr `{ … } >&2` (body byte-preserved), all **38** interactive reads → `/dev/tty` via tool-local `tty_read()` (EOF/no-tty → pointer + rc1, never hangs), `prompt_ipver` de-command-substituted so EOF exits gracefully; root gate / per-cmd confirm / typed RESET / pager / notify / every ufw invocation untouched. Both new tools register `# POS_SUBCMDS:` += `menu`; POS.md rows updated; GEN regen'd. Chain: Builder T4 (`reportAgents/2026-08-23-builder-t4-p2-menus-vbox-download.md`; correctly caught an Orchestrator brief error claiming download was in INTERACTIVE_CMDS) + T5 (`-t5-firewall-menu-migration.md`; pty parity captures vs pre-edit baseline) → Reviewer ACCEPT-WITH-NITS over both (`-reviewer-phase2-menu.md`, transcribed by Orchestrator; recursion/injection analysis, 13/13 mapping proof, four T5 intents verified hunk-by-hunk). Verified: bash -n ×3 + gates green after each pass; final trio re-run by Orchestrator post-T5 — `make check` OK · `make lint` 0 FAIL / 0 WARN (76s under box load ~7; the earlier apparent lint hang was shared-box CPU contention, no code issue). Remaining notes for later sessions: errexit kills whole menu when a backing verb hard-fails (repo-wide pattern, all six menus); `confirm()` EOF hits set-u unbound `yn` (pre-existing common.sh); vbox create EOF at dir prompt degrades to default while name/image prompts abort (cosmetic).
 - **2026-08-26** — `pos ai alias` activation rework (Option B) + `pos config` listing readability, per the 2026-08-26 Architect/Designer specs (`AgentsReport/{architect,designer}/2026-08-26-*.md`). **Alias activation:** the stale sourced-snapshot mechanism is gone — every `pos ai alias` invocation runs `_alias_sync()` (two-way reconciliation: render-diff-install of one executable wrapper per ENV record at `~/.local/bin/<name>` chmod 755 via mktemp+mv with a `bash -n` pre-commit guard; marker-guarded deletion of owned wrappers missing from ENV; legacy `ai-aliases.sh` generation stopped and generator-marker-guarded auto-removal with an `unalias <names>` remediation hint; loud PATH guidance when `~/.local/bin` is off PATH). Edits are live on next invocation with no shell reload (kills the reported stale-gemini-alias bug class); create refuses foreign-file and PATH-binary collisions; `show` gains the wrapper path; `pos-system-uninstall` sweeps the wrappers by their line-2 marker in discovery+removal. Dup-table menu bug fixed with a single `_alias_table` renderer (menu option 4 returns to the loop whose pre-render already shows fresh state). **Config readability** (`lib/config-ui.sh`, fully generic): new optional `# POS_CONFIG:` field types — `@Caption` / `@[KEY=v1|v2] Caption` group captions (condition evaluated per render via `cfg_value`; inactive groups dimmed with a textual reason, never hidden → numbering stable; empty-alt segment = unset-as-default) and `*providers=<tag>` adapter filtering (zero match warns once + suppresses its caption); uniform typography tier for ALL scopes (bold title/keys, CYAN rule, dim numbers/placeholders/examples/captions, hanging-indent wrap clamped 60–120 cols, whole render block → stderr per menu-lib house pattern, honest prompt `Number to edit [r=refresh, q=quit]:`); masking/edit flow byte-compatible, no per-scope branches. `bin/pos-ai` line-6 header adopted to the caption/tag syntax (single-line change). Verified: stub-PATH harness (`HOME=/tmp/…`, `CONFIG_DIR` seam, argv-capturing `pos` shim) covering %q quoting round-trips (quotes/backticks/`$()`/%/unicode), staleness kill-test, orphan retraction, collision-refusal matrix, legacy migration (marker + foreign), PATH-absent warning, non-tty guard, idempotent double-sync; rendered-output diffs vs Designer mockups for `ai` AND old-format `system`; gates `make gen && make check && make lint` 0 FAIL / 0 WARN.
 - **2026-08-27** — Critical fix: paste injection + multiline paste in `pos ai alias`'s Insert Prompt (root cause: `menu_ask_value` → plain line-oriented `read -rp`; a multi-line Ctrl+V paste floods the tty queue, `read` consumes only line one and the rest execute as commands later or get eaten by the next prompt — user-verified `$(whoami)`/`; ls`/`sudo apt update` behavior). New `menu_read_value()` in `lib/menu-lib.sh` (169→362): raw-mode (`stty -icanon -echo -isig min 1 time 0`) bracketed-paste-aware value reader — `\e[?2004h/l` markers, text inside `[200~…[201~` inserted LITERALLY (embedded newlines/CR are data), Enter submits only outside a paste, Backspace/DEL/Left/Right/Home/End/Delete/Ctrl-U edit, Ctrl-D-on-empty + Ctrl-C/Z/\ cancel (terminal restored first); bytes read chunk-wise via `dd bs=4096|od -tx1|tr` — NOT bash's `read` builtin, which self-interrupts on an ETX byte from a tty even with ISIG disabled (SIGINTs the whole script on Ctrl-C); confirmed `read -erp` (readline) atomically consumes a paste but returns only its first line, so a custom reader was required. `bin/pos-ai-alias` (712→760): `_alias_prompt_encode/_decode` (backslash→`\\`, newline→`\n`; literal `[ = ]` comparisons — bash `case` patterns don't match a single backslash), `_alias_prompt_truncate` newline-safe + max-length arg; load/save encode/decode the prompt field; edit wizard shows a truncated display default but Enter restores the FULL original prompt (fixes pre-existing silent truncation of >80-char prompts), empty-original Enter continues. Verified: pty harnesses (`/tmp/pty_{menulib,cancel,e2e_alias}.py`, `/tmp/roundtrip_test.sh`) — bracketed multiline paste captured verbatim incl. `C:\temp\note`/`$(whoami)`/`; ls`/`echo test`/`sudo apt update`, nothing executed, clean exit; single-line paste; Ctrl-D and Ctrl-C both cancel cleanly (CANCELLED→DONE, terminal restored); full create→list→show→edit E2E with decode round-trip and Enter-keeps-full; `bash -n` ×2, `make gen && make check`, `make lint` 0 FAIL / 0 WARN.
+- **2026-08-27** — Configurable AI-bridge trigger word for the Telegram listener: the hard-coded `ai ` prefix in `pos-communication-telegram-listener` became `TELEGRAM_AI_PREFIX` (default `ai`) — messages starting with `<prefix> ` (case-insensitive, literal match) are forwarded to Gemini. New `prefix` verb: `pos communication telegram listener prefix` shows the current word, `prefix <word>` sets it (validated `[A-Za-z0-9][A-Za-z0-9_-]*`, writes `TELEGRAM_AI_PREFIX` to `telegram.env` chmod 600); also editable via `pos config telegram` (field added to the sender's `# POS_CONFIG:` telegram scope — registry-driven, no code in config-ui). Matching is per-message hot-reloaded (like the command map — no daemon restart), via scoped `shopt -s nocasematch` + quoted-literal `=~` prefix (bash `case` patterns can't do literal-then-whitespace + case-insensitivity in one test); `ai_bridge_prefix()` precedence: telegram.env > env from load_config > default `ai`. `--status` shows the current prefix; usage + `# POS_SUBCMDS: prefix` added (completions regenerate). Preserved edge: bare `ai` (no trailing space) never matched the old regex, so it still falls through to "Unknown command". Docs: POS.md listener rows/paragraph, howto/ai.md Telegram section + troubleshooting (also corrected a stale claim that AI errors reply with a `pos config ai` hint — code replies `AI error: …` only). Verified: function-level routing harness (`/tmp/ai_prefix_routing_test.sh` — extraction of the real listener functions + PATH stub `pos`): default `ai`/`AI` routes, bare-prefix and unknown-command fallthrough, `ai /reset` and custom-`bot` `/reset` reset the session, custom `bot`/`BOT` routes and old `ai` no longer routes, per-message hot-reload after removing the var; CLI verb tests (show/set/invalid rc 1/leading-digit/`--status`); dispatch smoke `pos communication telegram listener prefix` + flat form; `pos config telegram` render shows the field; `bash -n` ×2, `make gen && make check`, `make lint` 0 FAIL / 0 WARN.