Split manifest internals behind the existing public facade

[bcomnes]

Summary

Closes #298.
This is an independent, behavior-preserving extraction based on master.

• Keep lib/domstack-manifest/index.js as the compatible public facade.
• Separate schema/derived types, settings normalization, record metadata, reconciliation, hashing, and hook/file I/O modules.
• Preserve dependency direction without runtime circular imports.

Validation

• Full npm test passed outside the restricted runner.
• npm run build:schema produced no schema diff.
• Built declarations and packed the package with lifecycle scripts disabled; all extracted modules and declarations are included.
• Compared packed runtime exports and schema values against the pre-extraction module: identical.
• A generic manifest consumer compiles before and after with skipLibCheck enabled.
• Strict declaration checking reports the same seven existing diagnostics before and after: undeclared HTML/Markdown builder T, four cpx2 declaration conflicts, and the installed thread-stream/Node type mismatch.
  These remain separate from this extraction and the consumer-types work tracked in Published v12 declarations fail strict consumer type-checking #291.
• Cleaned generated declarations with the repository cleanup scripts.

[github-actions]

Coverage Report for CI Build 34011309516

Coverage increased (+0.7%) to 94.858%

Details

• Coverage increased (+0.7%) from the base build.
• Patch coverage: 12 uncovered changes across 4 files (1054 of 1066 lines covered, 98.87%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
lib/domstack-manifest/hooks.js	60	52	86.67%
lib/domstack-manifest/records.js	211	209	99.05%
lib/domstack-manifest/hash.js	60	59	98.33%
lib/domstack-manifest/reconcile.js	280	279	99.64%
Total (7 files)	1066	1054	98.87%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	7328
Covered Lines:	7102
Line Coverage:	96.92%
Relevant Branches:	1540
Covered Branches:	1310
Branch Coverage:	85.06%
Branches in Coverage %:	Yes
Coverage Strength:	181.07 hits per line

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💛 - Coveralls

[bcomnes]

Is this redundant with code elsewhere in the project?