docs: design the portable solution architect agent

Record the direction and build plan for replacing the upstream
google-cloud-solution-architecture skill with a portable agent.

- ADR-0002: Agent Skills are the portable unit of behaviour, loaded by
  the framework's native skill runtime; discovery and grounding use
  each Cloud provider's hosted remote MCP servers.
- ADR-0003: LangGraph holds Execution state, checkpoints and
  interrupts; a ReAct Orchestrator and Specialists run as ADK
  LlmAgents with SkillToolset. Supersedes ADR-0001.
- CONTEXT.md: domain glossary (Execution, Phase, Approval, Revision,
  Orchestrator, Specialist, Deliverable, Dependency, Cloud provider).
- .scratch/solution-architect-agent/spec.md: build spec with the
  dependency graph, Revision rules, tool tiers, MCP allowlists, A2A
  interaction, tests and nine build increments.
- .scratch/phase-pipeline/spec.md: superseded; kept as decision log.
- CLAUDE.md and docs/agents/: agent skill configuration (local
  markdown issue tracker, triage labels, domain docs).
- README.md: direction note; flags current ADK classes as stubs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,19 @@
+# CLAUDE.md
+
+## Direction
+
+Before designing or restructuring agent code, read `docs/adr/`. ADR-0002 is the anchor: behaviour lives in Agent Skills (agentskills.io format) loaded by the framework's own skill runtime, and this repo builds the tooling around them. Google Cloud is the first Cloud provider, not the only one, so cloud-specific knowledge belongs in Skills and tooling, never in the agent's core. Reach cloud environments and cloud documentation through the provider's hosted remote MCP servers, not hand-written API clients. The current build plan is `.scratch/solution-architect-agent/spec.md`.
+
+## Agent skills
+
+### Issue tracker
+
+Issues and specs live as local markdown files under `.scratch/<feature-slug>/`. See `docs/agents/issue-tracker.md`.
+
+### Triage labels
+
+Default five-role vocabulary (`needs-triage`, `needs-info`, `ready-for-agent`, `ready-for-human`, `wontfix`), recorded as a `Status:` line in each issue file. See `docs/agents/triage-labels.md`.
+
+### Domain docs
+
+Single-context: one `CONTEXT.md` and `docs/adr/` at the repo root. See `docs/agents/domain.md`.