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/mcp/tools/milestones.py

@@ -57,9 +57,7 @@ async def get_milestone(milestone_id: int) -> dict:
     return {
         "milestone": out,
         "steps": [t.to_dict() for t in steps],
-        "applicable_rules": applicable["rules"],
-        "subscribed_rulebooks": applicable["subscribed_rulebooks"],
-        "applicable_rules_truncated": applicable["truncated"],
+        **rulebooks_svc.rules_payload(applicable),
     }