refactor: serialize manifests through one shared helper

[prisis]

Follow-up to #403 and #404 — based on #404's branch, so review it last; the base retargets automatically as those land.

Problem

Three packages each had their own "write a manifest back preserving its formatting" code, and two of them rewrote a CRLF manifest as LF — a whole-file diff in a release commit:

package	indent	trailing newline	line endings
multi-semantic-release (recognizeFormat + writeFileSync)	✅	✅	❌ LF
semantic-release-clean-package-json (writeJson({ detectIndent: true }))	✅	✅	❌ LF
semantic-release-pnpm (after #404)	✅	✅	✅

Three implementations meant fixing one fixed none of the others.

Fix

shared/serialize-manifest.ts holds the pnpm behaviour as a pure function — manifest in, string out — and all three packages call it. No new npm package: the folder is plain source that packem inlines into each dist at build time (verified: serializeManifest appears in the bundle of all three, with detect-indent and @visulima/fs/eol staying external).

Being pure also makes it usable from multi-semantic-release's synchronous updateManifestDeps, which the async writeJson-based approach could not be.

Fallout:

• recognizeFormat, its test, and the FileFormat / RecognizeFormatFunction types go with their only caller, as does the detect-newline dependency.
• detect-indent is added to semantic-release-clean-package-json (the other two already had it). Each package keeps declaring what the inlined code imports.
• The root manifest gains detect-indent and @visulima/fs so the shared file resolves its own imports under pnpm's isolated node_modules — without them tsc --noEmit fails on shared/serialize-manifest.ts.
• lint:prettier:root now also checks shared/*.ts. ESLint runs per package and does not reach the folder.

Behaviour change

multi-semantic-release previously appended the file's dominant newline whether or not the original ended with one; it now appends one only if the original did. That is the point of the helper — leave the file as it was found.

Tests

• packages/multi-semantic-release/__tests__/utils/serialize-manifest.test.ts — 8 cases covering indent, trailing newline, CRLF/LF and the no-original fallback. It replaces recognize-format.test.ts and covers the helper on behalf of all three packages, since the folder has no test project of its own.
• semantic-release-clean-package-json gains a CRLF round-trip test over publish — it fails on the old writeJson path.
• update-deps.test.ts 101/101, serialize-manifest 8/8, clean-package-json 6/6, semantic-release-pnpm 12/12. tsc --noEmit clean in all three; all three build.

multi-semantic-release.test.ts (23) and bin/cli.test.ts (2) fail in my sandbox — the fixture repos die on git fetch --tags with "couldn't find remote ref HEAD". I re-ran them against the base commit with the base dependency set: identical 23 failures, so they are environmental and not from this change.

🤖 Generated with Claude Code

https://claude.ai/code/session_01MqVjBDe8SkgMK7LpDpgjJ7

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[github-actions]

Thank you for following the naming conventions! 🙏

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.04%. Comparing base (cc3f5c1) to head (10ae82e).

Additional details and impacted files

@@                        Coverage Diff                        @@
##           fix/pnpm-prepare-single-write     #405      +/-   ##
=================================================================
+ Coverage                          84.37%   86.04%   +1.67%     
=================================================================
  Files                                 21       44      +23     
  Lines                                448     1362     +914     
  Branches                             108      356     +248     
=================================================================
+ Hits                                 378     1172     +794     
- Misses                                69      178     +109     
- Partials                               1       12      +11     

Flag	Coverage Δ
multi-semantic-release	87.64% <100.00%> (?)
semantic-release-clean-package-json	77.27% <100.00%> (?)
semantic-release-pnpm	84.30% <100.00%> (-0.08%)	⬇️

Files with missing lines	Coverage Δ
packages/multi-semantic-release/src/update-deps.ts	90.38% <100.00%> (ø)
...s/semantic-release-clean-package-json/src/index.ts	97.36% <100.00%> (ø)
packages/semantic-release-pnpm/src/prepare.ts	100.00% <100.00%> (ø)

... and 21 files with indirect coverage changes

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