fix(session): require config-backed mutation authority and workspace-bound targets (#714)

Close the #714 remediation gap left at 943d402 where env-only mutation
profiles, REMOTES Timesheet defaults treated as explicit caller input, and
machine-dependent Git remotes produced false greens.

- Fail closed when mutations lack a config-backed profile with non-empty
  allowed_repositories; env ops cannot invent mutation authority.
- Preserve omitted-vs-explicit org/repo provenance through the mutation
  gate; omitted targets bind to the verified workspace repository.
- Prefer workspace-aligned Git remotes over historical Timesheet defaults
  in MCP _resolve and CLI resolve_remote.
- Centralize deterministic config-backed mutation fixtures; migrate
  mutation tests off env-only authority without weakening security
  assertions.

Full suite: 2744 passed, 6 skipped.

tests/test_role_session_router.py

@@ -36,6 +36,7 @@ CONFIG = {
                 "gitea.pr.approve", "gitea.pr.merge", "gitea.pr.review",
             ],
             "execution_profile": "prgs-author",
+        "allowed_repositories": ["Scaled-Tech-Consulting/Gitea-Tools"],
         },
         "prgs-reviewer": {
             "enabled": True,
@@ -51,6 +52,7 @@ CONFIG = {
                 "gitea.pr.create", "gitea.branch.push", "gitea.issue.create",
             ],
             "execution_profile": "prgs-reviewer",
+        "allowed_repositories": ["Scaled-Tech-Consulting/Gitea-Tools"],
         },
         "prgs-merger": {
             "enabled": True,
@@ -65,6 +67,7 @@ CONFIG = {
                 "gitea.pr.create", "gitea.branch.push", "gitea.pr.approve",
             ],
             "execution_profile": "prgs-merger",
+        "allowed_repositories": ["Scaled-Tech-Consulting/Gitea-Tools"],
         },
         "prgs-reconciler": {
             "enabled": True,
@@ -81,6 +84,7 @@ CONFIG = {
                 "gitea.branch.push",
             ],
             "execution_profile": "prgs-reconciler",
+        "allowed_repositories": ["Scaled-Tech-Consulting/Gitea-Tools"],
         },
     },
     "rules": {"allow_runtime_switching": False},