Starter: add schema notes for Context Pack and Preflight Decision

[daishizenSensei]

Add concise spec notes explaining when agents should request a context pack and preflight decision.\n\nAcceptance:\n- Update spec docs.\n- Explain how these objects reduce context explosion.\n- corepack pnpm run lint:spec

guild@0.1.0 lint:spec /Users/quentinbrosseau/Documents/Codex/2026-04-24-you-re-an-expert-in-ai/guild
node scripts/validate-spec.mjs

ok spec/examples/taskpack.example.json
ok spec/examples/dri-binding.example.json
ok spec/examples/artifact.example.json
ok spec/examples/promotion-record.example.json
ok spec/examples/governance-policy.example.json
ok spec/examples/approval-request.example.json
ok spec/examples/promotion-gate.example.json
ok spec/examples/commons-entry.example.json
ok server/internal/bootstrap/fixtures/governance-policy.json
ok server/internal/bootstrap/fixtures/approval-request.json
ok server/internal/bootstrap/fixtures/promotion-gate.json
ok server/internal/bootstrap/fixtures/commons-entry.json
ok spec/examples/replay-bundle.example.json
ok spec/examples/workspace-constitution.example.json
ok spec/examples/context-pack.example.json
ok spec/examples/preflight-decision.example.json
ok server/internal/bootstrap/fixtures/taskpack.json
ok server/internal/bootstrap/fixtures/dri-binding.json
ok server/internal/bootstrap/fixtures/artifact.json
ok server/internal/bootstrap/fixtures/promotion-record.json and corepack pnpm run lint:docs

guild@0.1.0 lint:docs /Users/quentinbrosseau/Documents/Codex/2026-04-24-you-re-an-expert-in-ai/guild
node scripts/check-doc-links.mjs

ok 39 markdown files pass.