feat: command registry, alias wrapper scripts, config-ui readability

- lib/registry.sh: shared query API over POS_* headers (reg_scan, reg_list,
  reg_lookup, reg_tools_in, reg_each, reg_config_scopes/keys). Replaces
  per-consumer sed/grep header parsing.

- bin/pos-tree + bin/pos _pos_category_help(): migrated to registry API.
  Category help now shows [deps: ...] annotations. Tree output preserved.

- New optional headers # POS_DEPS: and # POS_EXAMPLES: in tool metadata.
  Added to pos-network-download (aria2c jq curl), pos-media-sync (lsblk jq),
  pos-system-backup (tar), pos-docker-ps (docker) as initial adopters.

- scripts/gen-docs.sh: extended tools array with deps/examples fields;
  conditional column rendering in gen_dispatch; deps annotation in gen_tree.
  Fixed URL-unsafe // joiner (→ middle dot ·) and \x1f caption delimiter
  collision in config-ui.

- bin/pos-ai-alias: rewrote activation from bash aliases (source-time-frozen)
  to executable wrapper scripts at ~/.local/bin. Staleness eliminated:
  edits apply on next invocation with no shell reload. _alias_sync()
  reconciliation on every subcommand, marker-guarded lifecycle, collision
  refusal, legacy .sh retirement. Fixed dup-table bug (option 4 no-op).

- lib/config-ui.sh: @caption/@[KEY=alt] conditional captions, *providers=<tag>
  tagged wildcards, uniform typography tier (bold/cyan/dim), honest prompt.
  Active provider keys bold, inactive dimmed with reason. Backward-compatible.

- bin/pos-system-uninstall: marker-scan for wrapper script cleanup.

- Docs synced: AGENTS.md (new headers + registry), DOC/SCRIPTS.md (registry
  section + lib list), DOC/POS.md (alias wrapper activation), MAINTENANCE.md
  (M-024). Lint fixed: pos-ai-alias registered in INTERACTIVE_CMDS.

Gates: make gen && make check && make lint = 0 FAIL, 0 WARN

bin/pos-system-uninstall

@@ -95,6 +95,15 @@ scan_tier1() {
     # User-local binaries
     [ -f "$HOME/.local/bin/pos-ai-hook.sh" ] && found+=("$HOME/.local/bin/pos-ai-hook.sh")
 
+    # pos ai alias wrapper scripts (marker-managed)
+    if [ -d "$HOME/.local/bin" ]; then
+        local awf
+        for awf in "$HOME/.local/bin"/*; do
+            [ -f "$awf" ] || continue
+            grep -q 'Managed by pos ai alias' "$awf" 2>/dev/null && found+=("$awf")
+        done
+    fi
+
     # Completion file
     [ -f /usr/local/share/bash-completion/completions/pos.bash ] && found+=("/usr/local/share/bash-completion/completions/pos.bash")
 
@@ -260,6 +269,17 @@ remove_tier1() {
     # User-local binaries
     [ -f "$HOME/.local/bin/pos-ai-hook.sh" ] && { rm -f "$HOME/.local/bin/pos-ai-hook.sh" && count=$((count+1)); }
 
+    # pos ai alias wrapper scripts (marker-managed only — foreign files untouched)
+    if [ -d "$HOME/.local/bin" ]; then
+        local arwf
+        for arwf in "$HOME/.local/bin"/*; do
+            [ -f "$arwf" ] || continue
+            if grep -q 'Managed by pos ai alias' "$arwf" 2>/dev/null; then
+                rm -f "$arwf" && count=$((count+1))
+            fi
+        done
+    fi
+
     # Completion file
     [ -f /usr/local/share/bash-completion/completions/pos.bash ] && { rm -f /usr/local/share/bash-completion/completions/pos.bash && count=$((count+1)); }