docs(claude): move ADR index and apply loop to lazy skills

[ThatRendle]

Why

The root CLAUDE.md loads into every session. At 36,175 chars it was costing ~9,000 tokens per session, and a large share of it was reference material only needed occasionally — plus one section pointing at tooling this repo doesn't have.

This trims it to 11,380 chars (~2,800 est. tokens, a ~6,200-token saving per session) without dropping any behavioural rule.

What moved

Content	New home	Why
ADR summary table (35 rows)	.claude/skills/adr-index/	Reference index over docs/adrs/; only the one-line skill description stays resident
OpenSpec apply-loop mechanics	.claude/skills/openspec-apply/	DEVLOG conventions, pre-flight, block carving, worker/reviewer loop, gates, supervisor review, done criteria — only needed during /opsx:apply
Pi-specific instructions	.pi/AGENT.md	Addressed to a different agent; now sits next to the .pi/skills and .pi/prompts it governs

What stays resident (deliberately)

Nothing safety-critical was moved behind lazy loading:

• The binding ADR rule — "Accepted ADRs must not be contradicted … write a superseding ADR" — and the docs/adrs/ADR-NNN-<slug>.md convention.
• The full Roles section, including "the main thread never writes feature code" and the reviewer-vs-supervisor distinction.
• The complete Stop and ask list.
• The standing Rules subsection.
• Out of scope for V1 in full.
• The TreatWarningsAsErrors prohibition.

CLAUDE.md states that the resident roles and prohibitions take precedence over the openspec-apply skill, preserving the original "this subsection is authoritative" intent.

What was deleted

• ## serena — serena is not a configured MCP server for this repo (it's registered only under the daemon workspace), so those were dead instructions that no session could act on.
• Derivable lines in ## Build and test and ## Code style: the standard dotnet build / dotnet test invocations, and the C# conventions an analyzer already enforces (PascalCase/camelCase, the I prefix, file-scoped namespaces). Kept the non-obvious ones — the env -u MEKO_API_KEY make test gotcha, openspec validate <slug> --strict, cancellationToken last-and-named, record vs class, and "no var when the type isn't obvious".

Notes

• No code changes; docs and agent-config only.
• Not an OpenSpec change — hence chore/ rather than change/.

🤖 Generated with Claude Code