refactor(mcp): one rules_payload() for every surface that hands rules to an agent; drop the dead bearer resolver (#2828, milestone 296 area 4)

Reading the 16 tool modules against each other: the six-key applicable-rules
block (applicable_rules, applicable_rules_truncated, subscribed_rulebooks,
project_rules, suppressed_rules, suppressed_topics) was hand-built in five
places — enter_project, get_project, get_task (legacy plans), get_milestone
(three of the six) and services/planning.start_planning. rulebooks_svc.
rules_payload() is now the one place that names them; get_milestone gains the
three it lacked, so every rules-carrying payload reads the same. list_rules /
list_always_on_rules share _rule_summary. mcp/auth.resolve_bearer_to_user_id
duplicated resolve_bearer's parsing and had no product caller (only its own
tests) — removed; the tests now exercise resolve_bearer.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scribe/services/planning.py

@@ -60,12 +60,7 @@ async def start_planning(user_id: int, project_id: int, title: str) -> dict:
 
     return {
         "milestone": milestone.to_dict(),
-        "applicable_rules": applicable["rules"],
-        "subscribed_rulebooks": applicable["subscribed_rulebooks"],
-        "applicable_rules_truncated": applicable["truncated"],
-        "project_rules": applicable.get("project_rules", []),
-        "suppressed_rules": applicable.get("suppressed_rules", []),
-        "suppressed_topics": applicable.get("suppressed_topics", []),
+        **rulebooks_svc.rules_payload(applicable),
         "project_goal": getattr(project, "goal", "") or "",
         "open_task_count": open_count,
     }

src/scribe/services/rulebooks.py

@@ -779,3 +779,22 @@ async def get_applicable_rules(
         "truncated": truncated,
         "subscribed_rulebooks": subscribed_rulebooks,
     }
+
+
+def rules_payload(applicable: dict) -> dict:
+    """The caller-facing shape of a get_applicable_rules() result.
+
+    Every surface that hands rules to an agent (enter_project, get_project,
+    get_milestone, get_task for legacy plans, start_planning) carries the
+    same six keys under the same names — so a reader learns them once. One
+    place renames `rules` → `applicable_rules` and `truncated` →
+    `applicable_rules_truncated`; the tools merge this into their payloads.
+    """
+    return {
+        "applicable_rules": applicable["rules"],
+        "applicable_rules_truncated": applicable["truncated"],
+        "subscribed_rulebooks": applicable["subscribed_rulebooks"],
+        "project_rules": applicable.get("project_rules", []),
+        "suppressed_rules": applicable.get("suppressed_rules", []),
+        "suppressed_topics": applicable.get("suppressed_topics", []),
+    }