fix(skill-author): fail loudly when scaffold repair cannot substitute

Why: repair_placeholders ran inside a command substitution, so a failing
sed left an emptied file behind and the script still exited 0 reporting
success.

- write via tmp file and abort on sed or mv failure
- re-check the target before moving staging into place
- stage in a dot-prefixed mktemp dir so a killed run leaves no fake skill
- source apm claims in deployment-modes.md; tag untyped code blocks

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KkT7RSDwDbmrM9T34b6sTi

plugins/kyberforge/.apm/skills/skill-author/SKILL.md

@@ -57,6 +57,6 @@ Gates `/factory-audit` enforces in both flows:
 
 Run `/factory-audit` on the resolved skill directory; resolve every FAIL before reporting done. It checks name-to-directory match, placeholders, both size budgets, boundary-target resolution and script hygiene — do not hand-check those. Hand-check the one thing it misses: an empty body reports `PASS  SKILL.md body word count 0 (ADR-0020 target: 600)`, so confirm at least one non-empty section exists.
 
-Versioning: on create, keep the scaffold's `0.1.0` — do not bump it (ADR-0022); on improve, bump the **patch** version.
+Versioning: on create, keep the scaffold's `0.1.0` — do not bump it (ADR-0022, Decision: `0.1.0` means "created and never yet revised"); on improve, bump the **patch** version.
 
 **Commit verification.** Inside a git worktree: once the audit is clean, run `rtk git add` and `rtk git commit` — do not stop at staging. Re-run `rtk git log --oneline -1` and confirm the hash changed from Step 1's. A non-empty `git diff --stat` is not proof: staged-but-uncommitted work is part of no commit and is silently lost if the tree is cleaned up. Report done only once the hash has changed. Outside a worktree (a skill under `~/.claude/skills/`, say) nothing is committable — report done on a clean audit, naming that as the reason.