chore: consolidate PR templates and hide style note in HTML comment

[yuranich]

What problem does this PR solve?

Two related problems with PR templates in this repo:

1. Template sprawl. The repo carries 21 PR template files. GitHub only auto-discovers templates at .github/PULL_REQUEST_TEMPLATE.md (default) or .github/PULL_REQUEST_TEMPLATE/<name>.md (selectable via ?template=). It does not look at packages/*/PULL_REQUEST_TEMPLATE.md. All 19 per-package files are invisible to GitHub; only the addon PR-creation tooling reads them. 7 were byte-identical to .github/PULL_REQUEST_TEMPLATE/addon.md, 8 more were identical copies of an orphaned generic template that nothing reads, and the remaining 4 (bci-whispercpp, cli, logging, nmtcpp) had incidental drift, not intentional variation.
2. Visible meta-instruction. Every PR opened against this repo started with a literal **Note**: be concise and prefer bullet points. line, because that meta-instruction sits as visible Markdown at the top of every template. It was authored as guidance for the PR author at fill-in time but ended up rendered into every PR body and copy-pasted forward by agents.

How does it solve it?

Consolidation:

• Delete all 19 packages/*/PULL_REQUEST_TEMPLATE.md files.
• Keep the two real templates: .github/PULL_REQUEST_TEMPLATE/sdk-pod.md and .github/PULL_REQUEST_TEMPLATE/addon.md.
• Add a minimal default .github/PULL_REQUEST_TEMPLATE.md (What problem / How does it solve it / Breaking changes) so PRs opened via the GitHub UI without ?template= get a usable body instead of nothing.
• Update the addon PR-creation tooling to point at the canonical template:
  • .cursor/skills/addon-pr-create/SKILL.md — now references .github/PULL_REQUEST_TEMPLATE/addon.md.
  • .claude/commands/addons/prepare_pr_description.md — same.
• The SDK pod skill already pointed at .github/PULL_REQUEST_TEMPLATE/sdk-pod.md; no change needed there.

Style-note cleanup:

• Replace the visible **Note**: line in .github/PULL_REQUEST_TEMPLATE/sdk-pod.md and .github/PULL_REQUEST_TEMPLATE/addon.md with an HTML comment containing the same style guidance.
• The new default template uses the same HTML-comment style guide.
• HTML comments are visible to anyone editing the template (humans and agents) but disappear in rendered Markdown, so generated PRs stay clean.

Breaking changes

None for end users or CI. For agent tooling: any custom workflow that read a per-package PULL_REQUEST_TEMPLATE.md directly must switch to .github/PULL_REQUEST_TEMPLATE/addon.md (or sdk-pod.md). The two known consumers are updated in this PR.

[yuranich]

/review

[github-actions]

Tier-based Approval Status

**PR Tier:** TIER1

**Current Status:** ✅ APPROVED

**Requirements:**
- 1 Team Member approval ✅ (2/1)
- 1 Team Lead OR Management approval ✅ (1/1)



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*This comment is automatically updated when reviews change.*

[github-actions]

❌ E2E Mobile Test Results - iOS

Overall Status: FAILED
Device Farm Result: UNKNOWN
Platform: iOS
Addon: @qvac/translation-nmtcpp
PR: #1924
Commit: de76439

Test Summary

Metric	Count
Total Tests	0
✅ Passed	0
❌ Failed	0
⏭️ Skipped	0

Links

• 🔗 Device Farm Run: View on AWS Device Farm
• 🔗 Workflow: View Details
• 📋 Run ARN: N/A

---

Automated E2E mobile testing powered by AWS Device Farm
Tests located in: test/mobile/

[github-actions]

❌ E2E Mobile Test Results - Android

Overall Status: FAILED
Device Farm Result: UNKNOWN
Platform: Android
Addon: @qvac/translation-nmtcpp
PR: #1924
Commit: de76439

Test Summary

Metric	Count
Total Tests	0
✅ Passed	0
❌ Failed	0
⏭️ Skipped	0

Links

• 🔗 Device Farm Run: View on AWS Device Farm
• 🔗 Workflow: View Details
• 📋 Run ARN: N/A

---

Automated E2E mobile testing powered by AWS Device Farm
Tests located in: test/mobile/

[github-actions]

❌ E2E Mobile Test Results - iOS

Overall Status: FAILED
Device Farm Result: UNKNOWN
Platform: iOS
Addon: @qvac/translation-nmtcpp
PR: #1924
Commit: b67352c

Test Summary

Metric	Count
Total Tests	0
✅ Passed	0
❌ Failed	0
⏭️ Skipped	0

Links

• 🔗 Device Farm Run: View on AWS Device Farm
• 🔗 Workflow: View Details
• 📋 Run ARN: N/A

---

Automated E2E mobile testing powered by AWS Device Farm
Tests located in: test/mobile/

[github-actions]

❌ E2E Mobile Test Results - Android

Overall Status: FAILED
Device Farm Result: UNKNOWN
Platform: Android
Addon: @qvac/translation-nmtcpp
PR: #1924
Commit: b67352c

Test Summary

Metric	Count
Total Tests	0
✅ Passed	0
❌ Failed	0
⏭️ Skipped	0

Links

• 🔗 Device Farm Run: View on AWS Device Farm
• 🔗 Workflow: View Details
• 📋 Run ARN: N/A

---

Automated E2E mobile testing powered by AWS Device Farm
Tests located in: test/mobile/

[github-actions]

❌ E2E Mobile Test Results - iOS

Overall Status: FAILED
Device Farm Result: UNKNOWN
Platform: iOS
Addon: @qvac/translation-nmtcpp
PR: #1924
Commit: 2b9a0cb

Test Summary

Metric	Count
Total Tests	0
✅ Passed	0
❌ Failed	0
⏭️ Skipped	0

Links

• 🔗 Device Farm Run: View on AWS Device Farm
• 🔗 Workflow: View Details
• 📋 Run ARN: N/A

---

Automated E2E mobile testing powered by AWS Device Farm
Tests located in: test/mobile/

[github-actions]

❌ E2E Mobile Test Results - Android

Overall Status: FAILED
Device Farm Result: UNKNOWN
Platform: Android
Addon: @qvac/translation-nmtcpp
PR: #1924
Commit: 2b9a0cb

Test Summary

Metric	Count
Total Tests	0
✅ Passed	0
❌ Failed	0
⏭️ Skipped	0

Links

• 🔗 Device Farm Run: View on AWS Device Farm
• 🔗 Workflow: View Details
• 📋 Run ARN: N/A

---

Automated E2E mobile testing powered by AWS Device Farm
Tests located in: test/mobile/