feat(project-bootstrap): canonical template + Step 5.6 add session-handoff trigger [v1.12.0]

CLAUDE.md.template gains `session handoff: read on start, write on end`
between `pull remote before work` and `follow project discipline`
(session-lifecycle clustering). Step 5.6 trigger->fulfiller table gains
the corresponding row (template ↔ table source-of-truth invariant).

Greenfield-bootstrap'ed projects now ship handoff trigger из коробки.
Existing projects unaffected — CLAUDE.md merge in Step 5 is idempotent
and respects user removals.

Bump 1.11.0 -> 1.12.0 MINOR (new canonical trigger = new capability,
backward-compatible). dist/project-bootstrap.skill rebuilt.

Closes [session-handoff-bootstrap-template-extend].
Unblocks [session-handoff-existing-projects-upgrade] Path B.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

skills/project-bootstrap/assets/CLAUDE.md.template

@@ -7,6 +7,7 @@ use project wiki
 use task management system
 check across all projects
 pull remote before work
+session handoff: read on start, write on end
 follow project discipline
 follow tdd-criteria
 delegate to interns when allowed