build(deps): migrate eslint 8 to 10 flat config + plugin updates

[megheaiulian]

Summary

Migrate from eslint 8 (eslintrc) to eslint 10 (flat config), plus update all eslint-related plugins to their latest majors.

Package changes

Package	From	To	Notes
eslint	8.57	^10.4	Flat config only, --ext removed
@typescript-eslint/* (2 pkgs)	7.18	typescript-eslint@^8 (1 pkg)	Unified package
eslint-plugin-unicorn	49	^72	2 rule renames, many new rules
eslint-plugin-jest	27	^29	Flat config via flat/recommended
eslint-config-prettier	9	^10	Flat config via /flat subpath
eslint-import-resolver-node	0.3	^0.4	exports-aware resolution by default
eslint-plugin-import	2.32	→ eslint-plugin-import-x@^4	Fork with eslint 10 support (upstream hasn't updated peer deps)
New: globals	—	^17	Replaces env: { node: true }
New: @eslint/js	—	^10	Provides js.configs.recommended

Config changes

• Delete .eslintrc.cjs + .eslintignore
• Create eslint.config.mjs (flat config)
• Lint script: drop --ext .ts,.js (extensions now via files globs)
• engines.node: >=20.19 → >=22 (unicorn v72 requires >=22)
• no-unused-vars: caughtErrors: "none" to preserve old behavior
• Ignore runtime/** (eslint --fix was modifying shipped runtime code)
• Disable many new unicorn v72 rules (too noisy for this project)
• Disable import-x/named (can't verify .ts named exports without type info)

Rule renames applied

Old	New
unicorn/prefer-json-parse-buffer	unicorn/consistent-json-file-read
unicorn/prevent-abbreviations	unicorn/name-replacements
import/no-unresolved (inline)	import-x/no-unresolved

Why eslint-plugin-import-x instead of eslint-plugin-import?

eslint-plugin-import@2.32 (latest) has peer dep eslint: ^8 || ^9 — doesn't support eslint 10. eslint-plugin-import-x is a maintained fork with identical rules, flat config support, and eslint 10 compatibility. Rule names use import-x/ prefix instead of import/.

Source changes (auto-fixed by eslint --fix)

• Removed unused eslint-disable comments (rules no longer triggered in v10)
• Updated import/no-unresolved → import-x/no-unresolved in inline comments
• Minor: split('.', 2) instead of split('.') in one test

No runtime behavior changes — all changes are in lint config and dev tooling.

Verification

• ✅ npm run lint — 0 errors, 1 harmless warning
• ✅ npm run build — rollup + type emit
• ✅ npm test — 4 suites, 114 tests, 314 snapshots pass (no snapshot changes)

What's NOT in this PR

• Type-aware linting (projectService: true) — deferred to a separate follow-up
• Fixing all new unicorn v72 rule violations — noisy/opinionated rules disabled for now, can be reviewed incrementally

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (024efa8) to head (d696089).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #154      +/-   ##
==========================================
- Coverage   98.97%   98.97%   -0.01%     
==========================================
  Files          36       36              
  Lines         974      973       -1     
  Branches      317      317              
==========================================
- Hits          964      963       -1     
  Misses         10       10              

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