QVAC-19908 chore[skiplog]: backmerge release-sdk-0.13.4 — version bump + changelog

[simon-iribarren]

🎯 What problem does this PR solve?

Lands the @qvac/sdk + @qvac/bare-sdk 0.13.4 release metadata on main,
per the gitflow "keep main aligned" rule. main is at 0.13.3, so without this
backmerge it would have a hole in its changelog history and its package.json
version would lag the published release. Merging this PR triggers the npm publish
of 0.13.4.

Companion release PR: #2681 (base release-sdk-0.13.4). This is the fix-only
0.13.4 release (Qwen hybrid tool-call recovery, #2677); the fix itself is already
on main, so this PR only brings the version bump + changelog.

📝 How does it solve it?

Cherry-picks the single release commit from release-sdk-0.13.4 (-x):

• packages/sdk/package.json — version 0.13.3 → 0.13.4
• packages/bare-sdk/package.json — version 0.13.3 → 0.13.4 (lockstep)
• packages/sdk/changelog/0.13.4/ — generated CHANGELOG.md, CHANGELOG_LLM.md
• packages/sdk/CHANGELOG.md — prepended aggregated 0.13.4 entry

Tagged [skiplog] so it does not generate a duplicate changelog entry on main.
Same shape as the previous backmerge, #2613 (release-sdk-0.13.3).

🧪 How was it tested?

• Clean git cherry-pick -x of the release commit onto upstream/main with no
  conflicts.
• git diff --stat upstream/main..HEAD confirms the change touches only the five
  expected release-metadata files and nothing else.

[simon-iribarren]

/review

[github-actions]

Tier-based Approval Status

**PR Tier:** TIER1

**Current Status:** ✅ APPROVED

**Requirements:**
- 1 Team Member approval ✅ (1/1)
- 1 Team Lead OR Management approval ✅ (1/1)



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