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).

skills/architecture-design/SKILL.md

@@ -0,0 +1,78 @@
+---
+name: architecture-design
+description: Architecture decision process — structured approach to system design decisions
+version: "1.0"
+owner: Architect
+prerequisites: requirements understood, constraints identified
+---
+
+# Architecture Design
+
+## When to use this skill
+
+- Deciding system boundaries, interfaces, or component ownership
+- Evaluating architectural alternatives
+- Establishing new patterns or constraints
+
+## Core methodology
+
+```text
+UNDERSTAND → IDENTIFY DECISION → GENERATE OPTIONS → EVALUATE → DECIDE → RECORD
+```
+
+## Step-by-step procedure
+
+### 1. Understand the context
+- What problem are we solving?
+- What are the constraints (technical, organizational, time)?
+- What existing architecture does this interact with?
+
+### 2. Identify the decision
+- What exactly needs to be decided?
+- What are the boundaries of this decision?
+- Who are the stakeholders?
+
+### 3. Generate options
+- Aim for 2-4 concrete options
+- Each option should be distinct (not variations of the same idea)
+- For each: what does it optimize for? What does it sacrifice?
+
+### 4. Evaluate options
+For each option, assess:
+- **Fit**: does it solve the stated problem?
+- **Complexity**: how much does it add?
+- **Reversibility**: how hard is it to change later?
+- **Risk**: what could go wrong?
+- **Evidence**: what supports this choice?
+
+### 5. Decide
+- Choose one option with clear rationale
+- State what is explicitly out of scope
+- Identify what would make you revisit this decision
+
+### 6. Record
+- Write an ADR in `memory/decisions/`
+- Update `memory/architecture/` if boundaries change
+- Link to related decisions
+
+## Common pitfalls
+
+- Deciding without evidence (opinion-driven design)
+- Over-architecting for imagined future needs
+- Not recording the decision (lost institutional knowledge)
+- Ignoring existing patterns (inconsistency)
+- Making reversible decisions with irreversible processes
+
+## Evidence requirements
+
+- Problem statement with constraints
+- Options considered with trade-offs
+- Decision rationale
+- Recording in ADR format
+
+## Exit criteria
+
+- Decision made and recorded
+- Alternatives documented with rationale
+- Impact on existing architecture assessed
+- Stakeholders can find the decision