Combine version and release skills into a single deploy skill

[sebastientaggart]

Merges the separate version and release skills into a unified deploy skill that handles both version bumping and GitHub release creation in a single workflow.

• Removes skills/version.md and skills/release.md, replaced by skills/deploy.md
• Adds generated adapter files for all platforms (Claude, Cursor, Gemini, Agents)
• Updates docs, config schema, README, and templates to reflect the consolidated skill

[sebastientaggart]

Review Summary

Verdict: APPROVE

Findings

• [NOTE] Minor duplication in skills/deploy.md — the {{#if BRANCH_DEV}} {{#if !BRANCH_TEST}} and {{#if BRANCH_TEST}} branches in Step 4 (Compute release contents) both emit the identical text: "Use the PR/issue list already computed in Step 2. If the version bump added new commits, re-fetch if needed." These could be collapsed into a single {{#if BRANCH_DEV}} block without the inner conditional, but it is functionally correct as-is.

No blocking issues found. The PR correctly:

1. Merges skills/version.md and skills/release.md into a single skills/deploy.md with proper Handlebars conditionals for all three branching modes (trunk, two-branch, three-branch).
2. Deletes the old version and release adapter files across all four platforms (Claude, Cursor, Gemini, Agents) and adds the new deploy equivalents.
3. Updates all cross-references in setup.md, ship.md, AGENTS.md.template, config schema, README, and docs — no stale /version or /release references remain (the one mention in docs/skills/deploy.md is intentionally historical context explaining the consolidation).
4. Config schema used_in arrays are correctly updated from [version]/[release] to [deploy].
5. The combined workflow preserves both human gates (version bump prompt + release confirmation) and all branching-mode-specific behavior from the original two skills.