Re-add disable-model-invocation to action skills once upstream bugs are fixed

Context

In v2.2.0 we removed disable-model-invocation: true from all 25 action skills (push, merge, init, etc.) because the flag is broken for plugin skills in Claude Code.

See commit 1eee461.

Upstream Bugs to Track

All of these need to be resolved before we can re-add the flag:

1. anthropics/claude-code#22345 — disable-model-invocation is ignored for plugin skills. Skill descriptions are loaded into context regardless, so the flag provides no benefit.

2. anthropics/claude-code#24042 — Skills with disable-model-invocation: true that appear in autocomplete fail when selected. Users get: "Skill X cannot be used with Skill tool due to disable-model-invocation". The flag blocks both model AND user invocation.

3. anthropics/claude-code#18949 — Plugin skills don't appear in slash command autocomplete at all (only commands/*.md files do). Even typing the full skill name (e.g., /ccmagic:push) returns "Unknown skill". This means users cannot directly invoke ANY plugin skills via slash commands — they must ask the model to invoke skills on their behalf via the Skill tool.

4. anthropics/claude-code#26251 (closed as dup of #24042) — Additional report confirming that disable-model-invocation prevents user invocation via slash command.

Current State (v2.2.0)

Without disable-model-invocation, Claude may auto-trigger action skills like /push, /merge, /init that have side effects. This is the trade-off we accepted — user access to all skills is more important than preventing auto-invocation.

Action Items

• Monitor upstream issues for fixes
• Once #22345 and #24042 are both resolved, re-add disable-model-invocation: true to action skills
• Once #18949 is resolved, verify that plugin skills appear in autocomplete and can be user-invoked via /
• Skills to re-flag: add-backlog, checkpoint, codex-review, complete-task, context-load, context-save, create-features, create-spike, create-tasks, debug, handoff, init, map-codebase, merge, plan, pr, push, quick-start, quick, resume, settings, start-spike, start-task, sync, verify

Start by reviewing commit 1eee461 and the listed action skills: add-backlog, checkpoint, codex-review, complete-task, context-load, context-save, create-features, create-spike, create-tasks, debug, handoff, init, map-codebase, merge, plan, pr, push, quick-start, quick, resume, settings, start-spike, start-task, sync, and verify. Monitor upstream issues #22345, #24042, and #18949; done means the relevant fixes are available, the flag is restored to those skills, and user invocation and autocomplete work as expected.