feat(inception): always-on exclusions reach every rule surface — list_always_on_rules(project_id), get_applicable_rules, rules_payload.excluded_always_on, session context, exclude/include tools (#2880, milestone 297 step 2)

A project that opted out of an always-on rulebook at inception must not see
it anywhere: list_always_on_rules(project_id=) and the subscription-derived
set skip it (an exclusion is total), get_applicable_rules / rules_payload
carry `excluded_always_on` as the seventh key so the departure is visible
wherever the rules are, and the SessionStart block built for a bound project
names it ("Excluded for this project by its inception decision …"). MCP:
list_always_on_rules takes project_id; exclude_always_on_rulebook /
include_always_on_rulebook mirror suppress/unsuppress (owner-only; the
rulebook must be always_on — subscribed rulebooks are left by unsubscribing).

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

tests/test_mcp_tool_rulebooks.py

@@ -175,6 +175,9 @@ def test_register_attaches_all_sixteen_tools():
     assert "create_rule" in mcp.names
     assert "subscribe_project_to_rulebook" in mcp.names
     assert "list_always_on_rules" in mcp.names
+    # milestone 297: a project's opt-out of a whole always-on rulebook
+    assert "exclude_always_on_rulebook" in mcp.names
+    assert "include_always_on_rulebook" in mcp.names
     assert "create_project_rule" in mcp.names
     assert "suppress_rule_for_project" in mcp.names
     assert "unsuppress_rule_for_project" in mcp.names