feat(conventions): generalize defaults, backfill old projects, adopt the standard in-repo

Harden the architectural-conventions standard so it works out-of-the-box on
any project and resolves for projects that predate it, and make RoboCo pass
its own gate.

General defaults (apply to every project, not just one with a tuned file):
- The auto-scan excludes test and documentation trees (tests/, docs/) — those
  legitimately define fixtures and aren't enforced code.
- Helper placement seeds at warn, not block: `helper` matches any top-level
  function, too blunt a signal to hard-block a route file's small private glue.
  Misplaced model/route/component stay block; the body-level thin_routes check
  remains the real fat-handler guard.
- thin_routes no longer counts transaction-lifecycle calls (commit/flush/
  refresh) as data access — an explicit `db.commit()` after delegating to a
  service is a valid pattern.
- no_lint_suppressions exempts a small allowlist of structurally-unavoidable
  framework codes (ruff TC001-TC003, pydantic prop-decorator); bare or other
  suppressions still flag.
- CLAUDE.md rule-lifting skips bare common-word tokens that would match
  everywhere (e.g. "commit"), keeping only specific identifiers.
- The ambient prompt block lists only constrained modules and truncates at a
  line boundary with a "+N more" pointer instead of cutting mid-line.

Backfill: the standard previously read the committed file + repo scan from
project.workspace_path, a field only a manual API call set — so an older
project (or one whose workspace was cleared) showed an empty "missing" map no
matter what was pushed. The service now ensures a dedicated, default-branch
read clone on demand (WorkspaceService.ensure_read_clone) and resolves from
it, persisting the resolved path + real HEAD. The panel tab, the spawn-time
ambient block, and the per-task constraints all resolve the committed standard
with no manual setup.

Adopt in-repo: relocate the inline request/response models from the system and
*_live route modules into roboco/api/schemas/ so the codebase passes its own
placement gate, and ship a canonical .roboco/conventions.yml. no_models_in_routes
and modular_cohesion are now clean and enforced at block.

Docs updated across the user guide, the agent-facing RAG standard, the
developer and pr_reviewer role prompts, CLAUDE.md, and the changelog. New unit
tests cover the scan exclusions, helper-warn, the suppression allowlist, the
commit exemption, and the resolve/backfill path; the conventions + project
integration suites pass against Postgres.

tests/unit/services/test_conventions_resolve.py

@@ -0,0 +1,66 @@
+"""ConventionsService root/HEAD resolution + backfill persistence (no DB)."""
+
+from __future__ import annotations
+
+import subprocess
+from types import SimpleNamespace
+from typing import TYPE_CHECKING
+
+from roboco.services.conventions import ConventionsService
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def _git_repo(root: Path) -> str:
+    (root / "roboco" / "services").mkdir(parents=True)
+    (root / "roboco" / "services" / "x.py").write_text("def f():\n    return 1\n")
+    for cmd in (
+        ["git", "init", "-q"],
+        ["git", "add", "-A"],
+        ["git", "-c", "user.email=t@t", "-c", "user.name=t", "commit", "-qm", "i"],
+    ):
+        subprocess.run(cmd, cwd=root, check=True, capture_output=True)
+    return subprocess.run(
+        ["git", "rev-parse", "HEAD"],
+        cwd=root,
+        capture_output=True,
+        text=True,
+        check=False,
+    ).stdout.strip()
+
+
+def _svc() -> ConventionsService:
+    return ConventionsService(session=None)  # type: ignore[arg-type]
+
+
+def test_resolve_reads_clone_head_and_backfills(tmp_path: Path) -> None:
+    sha = _git_repo(tmp_path)
+    project = SimpleNamespace(workspace_path=None, head_commit=None, slug="p")
+    root, head = _svc()._resolve(project, tmp_path)
+    assert root == tmp_path
+    assert head == sha
+    # The backfill: the resolved path + real HEAD are persisted on the project.
+    assert project.workspace_path == str(tmp_path)
+    assert project.head_commit == sha
+
+
+def test_resolve_non_git_path_keeps_persisted_head(tmp_path: Path) -> None:
+    project = SimpleNamespace(
+        workspace_path=str(tmp_path), head_commit="deadbeef", slug="p"
+    )
+    _root, head = _svc()._resolve(project, None)
+    # A non-git legacy path must not clobber the persisted head_commit.
+    assert head == "deadbeef"
+    assert project.head_commit == "deadbeef"
+
+
+def test_resolve_no_workspace_returns_none_root() -> None:
+    project = SimpleNamespace(workspace_path=None, head_commit=None, slug="p")
+    root, head = _svc()._resolve(project, None)
+    assert root is None
+    assert head == "HEAD"
+
+
+def test_head_sha_at_non_git_returns_none(tmp_path: Path) -> None:
+    assert ConventionsService._head_sha_at(tmp_path) is None