Phase 1-3: Add memory, skills, and improvement systems

- memory/: cross-session project memory with decisions, lessons, failures,
  architecture, and sessions categories. Each has format templates and
  lifecycle documentation.
- skills/: 12 reusable specialized methodologies (tdd, systematic-debugging,
  architecture-design, code-review, security-review, repository-analysis,
  failure-analysis, refactoring, test-analysis, incident-investigation,
  browser-automation, research). Each has frontmatter and methodology sections.
- improvements/: proposal-based improvement system requiring human approval.
- scripts/memory-lifecycle.sh: deterministic memory operations (recall, store,
  list, search, sessions, cleanup).
- scripts/test-memory-system.sh: 12 structural tests for all new systems.
- orchestrator.md: added Memory Recall stage, Learning and Memory Storage
  stage, Improvement Proposals workflow, memory/skills rules, and 3 new
  actions (A23-A27) to the action catalog. Updated behavioral acceptance test
  and state separation model.
- All 12 subagents: added Memory & Skills Awareness sections with recall
  and store instructions.
- docs/AGENT_ARCHITECTURE.md: documented memory, skills, and improvements
  systems (sections 12-14). Updated action count (27), state model, and
  remaining weaknesses.
- README.md: documented new systems, updated repository layout, added
  test-memory-system.sh documentation.

All 39 tests pass (16 architecture + 12 memory + 11 bootstrap).

memory/lessons/README.md

@@ -0,0 +1,30 @@
+# Implementation Lessons
+
+Reusable knowledge discovered during implementation work.
+
+## Format
+
+```markdown
+# Lesson-NNNN: <title>
+
+Date: YYYY-MM-DD
+Author: <agent>
+Context: <what task/situation>
+Recurring: yes | no
+
+## What was learned
+
+<the lesson>
+
+## Application
+
+<when/how this applies to future work>
+
+## Evidence
+
+<supporting evidence — file:line, commands, outputs>
+```
+
+## Index
+
+_No lessons recorded yet._