Fix published v12 declaration compatibility

[bcomnes]

Summary

• Emit valid concrete HTML and Markdown builder declarations without an undeclared generic.
• Replace implementation-derived copy report and logger types with local structural contracts.
• Add a packed-tarball consumer test covering root and public type imports under TypeScript 5.9 and 6.0 with NodeNext resolution and skipLibCheck: false.
• Clean generated declaration artifacts after the packed-consumer test.

Validation

• npm test
• The packed artifact installs and compiles in a clean consumer under TypeScript 5.9 and 6.0.

Fixes #291.

[coveralls]

Coverage Report for CI Build 34011220579

Coverage increased (+0.1%) to 94.297%

Details

• Coverage increased (+0.1%) from the base build.
• Patch coverage: 28 of 28 lines across 6 files are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	7324
Covered Lines:	7098
Line Coverage:	96.91%
Relevant Branches:	1706
Covered Branches:	1417
Branch Coverage:	83.06%
Branches in Coverage %:	Yes
Coverage Strength:	182.52 hits per line

---

💛 - Coveralls

[bcomnes]

Are we losing type resolution here?