Add AgentGit M1: agent-native git layer over a Forgejo backend

AgentGit is a thin, DID-gated source-collaboration layer over a backend
forge (default Forgejo at git.profullstack.com, BBS-members-only) — not a
new git host. M1 implements the contract and engines:

- forge/adapter.ts: ForgeAdapter interface (only forge-specific surface)
- forge/forgejo.ts: ForgejoAdapter over Forgejo/Gitea REST v1 (injectable
  fetch, typed errors), incl. ensureUser for member provisioning
- access.ts: gateAccess DID membership gate (owner/role/visibility)
- merge-policy.ts: evaluateMergePolicy pure engine (reviews, reputation
  floor, checks, escrow, merge method, agent-merge toggle)
- service.ts: AgentGitService ties gate + policy to the adapter; refuses
  policy-failing merges; provisionMember hook for AgentBBS
- schemas: logicsrc-repo + logicsrc-pull-request, registered in
  @logicsrc/validators with fixtures
- docs/agentgit.md spec; plugin wired into root build (default/disabled)

27 vitest tests pass; full monorepo build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/schemas/fixtures/pull-request.yaml

@@ -0,0 +1,24 @@
+type: logicsrc.pull_request
+version: "1.0"
+repo: agentgit-demo
+number: 7
+title: Add Forgejo backend adapter
+description: Implements the M1 ForgeAdapter against the Forgejo REST API.
+author_did: contributor.profullstack
+source_branch: feat/forgejo-adapter
+target_branch: main
+head_sha: abc1234
+task: task-42
+status: approved
+checks:
+  - name: ci
+    status: passing
+    url: https://git.profullstack.com/owner/agentgit-demo/actions
+reviews:
+  - reviewer_did: maintainer.profullstack
+    decision: approve
+    reputation: 25
+    summary: Looks good, policy-gated merge verified.
+    created_at: 2026-06-14T01:00:00Z
+created_at: 2026-06-14T00:30:00Z
+updated_at: 2026-06-14T01:05:00Z

packages/schemas/fixtures/repo.yaml

@@ -0,0 +1,27 @@
+type: logicsrc.repo
+version: "1.0"
+name: AgentGit Demo
+slug: agentgit-demo
+description: Reference AgentGit repository hosted on git.profullstack.com.
+owner_did: owner.profullstack
+board: /agentgit
+visibility: members_only
+default_branch: main
+backend:
+  provider: forgejo
+  url: https://git.profullstack.com
+  external_id: owner/agentgit-demo
+members:
+  - did: maintainer.profullstack
+    role: maintainer
+  - did: contributor.profullstack
+    role: contributor
+merge_policy:
+  min_reviews: 1
+  require_passing_checks: true
+  reviewer_reputation_min: 0
+  escrow_required: false
+  allow_agent_merge: true
+  allowed_merge_methods:
+    - squash
+created_at: 2026-06-14T00:00:00Z