feat(forge): Phases 2+2.1+3 — Gitea + GitLab providers, per-call routing, local-merge fallback (#575)

* feat(forge): Phase 2 — Gitea provider, per-call routing, host registry

Gitea support lands behind the Phase-1 seam:

- GiteaProvider (services/forge/gitea.py): Gitea v1 transport addressed
  by instance host (api base from the project's git_url). Where Gitea's
  wire contract diverges from GitHub's, the provider adapts responses
  back into the shapes GitService already classifies (ShapedResponse):
  `token` auth scheme, duplicate-PR 409→422 with the "already exists"
  text GitService keys on, commit statuses reshaped into check_runs /
  workflow_runs envelopes, APPROVE→APPROVED review mapping, Do-keyed
  POST merge, merge-method repo keys, label-color '#' prefix,
  client-side head/base PR filtering. Deliberate postures per the spec:
  zero-workflows fail-open (statuses-free repo → no_ci_configured) and
  merge_branch as a shaped 501 (env-sync cascade lands on missing_ref;
  the shared local-git fallback is Phase-2.1).
- ForgeRouter (services/forge/router.py): GitService._forge now routes
  per call from RepoRef.host — every existing call site unchanged in
  shape. RepoRef gains an optional host; _parse_git_url returns the
  host-stamped ref and it is threaded through GitService/release
  executor instead of being rebuilt from strings (helpers re-signatured
  to take RepoRef).
- Host registry (services/forge/registry.py): in-memory host→provider
  map, self-healing — ProjectService.get/get_by_slug re-register on
  every read; provider_for resolves gitea projects by git_url host.
- Registration validation now accepts git_provider="gitea"; GitLab
  remains recognized-but-rejected. Panel: the read-only Forge badge
  becomes a real picker (Auto-detect / GitHub-GHE / Gitea / GitLab
  disabled).

Plain git (clone/fetch/push) needs no changes — the Basic-auth
extraheader works on Gitea unchanged. Gates: mypy 392 files, xenon A,
full unit suite 6356 green, integration suite 2257 green.

* feat(forge): live-Gitea contract suite + scheme support + slash-safe refs

Hardening from running the provider against a real dockerized Gitea
1.22.6 (the spec's Phase-2 contract suite, now committed as the
env-gated tests/e2e_smoke/test_gitea_live.py — self-seeding: creates its
own repo, pushes real commits, and drives PR open → duplicate reshape →
list/filter → diff → review → labels → commit-status CI reshapes →
squash merge → branch delete → release, plus a live verification of the
x-access-token Basic-auth git-CLI claim).

Two real findings fixed:
- Branch refs weren't URL-encoded — every RoboCo branch carries slashes
  (feature/backend/...), and Gitea's router 404s on the extra path
  segments. list_ci_runs + delete_branch_ref now quote the ref
  (regression-pinned in the unit suite).
- The API base hardcoded https; a LAN instance serving plain http is a
  real deployment shape. GiteaProvider gains a scheme (recorded per host
  by the registry from the project's git_url).

ShapedResponse moves to forge/shaping.py (shared by the upcoming GitLab
transport, which needs its text override for diff reassembly).

* feat(forge): Phase 3 GitLab provider + Phase 2.1 local-merge fallback

GitLabProvider (services/forge/gitlab.py): GitLab v4 transport addressed
by host+scheme, subgroup-safe (the MR project path packs into
RepoRef.owner, URL-encoded per call). Adapters translate MR semantics
into the GitHub shapes GitService classifies: iid→number,
source/target_branch→head/base with a merged bool, per-file diffs
reassembled into unified-diff text (ShapedResponse text override,
3-page cap), approve-vs-note review routing (GitLab has no
request-changes verb), pipelines/statuses reshaped into
workflow_runs/check_runs, merge-method repo-key mapping, duplicate-MR
409→422. Reviewer mirroring is skipped (needs numeric ids RoboCo
doesn't store); provisioning stays Phase 4. gitlab.com now auto-detects
at registration like github.com; self-hosted GitLab sets the provider
explicitly (panel picker enabled).

Phase 2.1: neither Gitea nor GitLab has GitHub's server-side merges
API — their merge_branch returns a shaped 501 and
GitService.sync_env_branch now runs the shared local-git fallback
(_local_merge_branch: throwaway clone → ancestor check → merge → push;
a conflict aborts with the remote untouched; same status vocabulary as
the merges-API path).

Also aligns the whole tree with the full gate's tests/-scoped mypy
(provider-test responder typing, e2e_smoke's stale owner/repo shapes).
Gates: mypy 1229 files clean, xenon A, unit suite 6393 green, forge
suites 85 green, panel typecheck/lint clean.

---------

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

tests/integration/test_git_conventions_pr.py

@@ -10,6 +10,7 @@ from uuid import uuid4
 from roboco.config import settings
 from roboco.db.tables import AgentTable, ProjectTable
 from roboco.models import AgentRole, AgentStatus, Team
+from roboco.services.forge import RepoRef
 from roboco.services.git import _ConventionsPr, get_git_service
 
 if TYPE_CHECKING:
@@ -144,7 +145,9 @@ async def test_open_conventions_pr_force_pushes_scaffold_branch(
 
     monkeypatch.setattr(git, "_token_for_project", _fake_token)
     monkeypatch.setattr(git, "push", _fake_push)
-    monkeypatch.setattr(git, "_parse_github_remote", lambda _ws: ("owner", "repo"))
+    monkeypatch.setattr(
+        git, "_parse_github_remote", lambda _ws: RepoRef("owner", "repo")
+    )
 
     _pr_number = 42
     _pr_url = "https://github.com/owner/repo/pull/42"
@@ -155,7 +158,7 @@ async def test_open_conventions_pr_force_pushes_scaffold_branch(
         def json(self) -> dict[str, object]:
             return {"number": _pr_number, "html_url": _pr_url}
 
-    async def _fake_post_pr(_owner: str, _repo: str, _token: str, _body: Any) -> _Resp:
+    async def _fake_post_pr(_repo_ref: RepoRef, _token: str, _body: Any) -> _Resp:
         return _Resp()
 
     monkeypatch.setattr(git, "_post_pr", _fake_post_pr)