feat(#1866): agent-side self-load of configured agent_skills

Each of the 22 consumer agents now self-loads its configured agent_skills
in its mandatory init step, so .planning/config.json agent_skills.<type>
reaches the agent on every runtime — including Cursor and /gsd-autonomous,
where Skill()-delegated workflow bash init did not reliably execute.

- gsd-core/references/agent-skills-bootstrap.md: shared contract
  (query + Read + dedup guard that skips when <agent_skills> is already
  in the prompt, so Claude's orchestrator-side injection never doubles)
- 22 agents/gsd-*.md: one self-load line naming the agent's own type
- gsd-core/workflows/autonomous.md: note that delegated agents self-load
- tests/agent-skills-bootstrap.test.cjs: regression + parity (CONSUMER_AGENTS
  bijection + fast-check property) — Generative-Fix-Divergence guard
- docs: ADR-1866, CONFIGURATION dual-injection How It Works, INVENTORY
  row, Changed changeset

Closes #1866

docs/INVENTORY-MANIFEST.json

@@ -200,6 +200,7 @@
     ],
     "references": [
       "agent-contracts.md",
+      "agent-skills-bootstrap.md",
       "ai-evals.md",
       "ai-frameworks.md",
       "artifact-types.md",
@@ -325,9 +326,9 @@
       "docs.cjs",
       "drift.cjs",
       "edge-probe.cjs",
+      "embedding-adapter.cjs",
       "eval-command-router.cjs",
       "eval.cjs",
-      "embedding-adapter.cjs",
       "external-descriptor-trust.cjs",
       "fallow-runner.cjs",
       "federated-config.cjs",