✨ Add npm run fix aggregator for the fix:* scripts

Override the prior design choice: there is now an npm run fix
script that runs fix:oxlint && fix:oxfmt. Rationale: the friction
of having to remember and run two separate fix commands after
npm run check outweighs the 'intentional fixes' argument once
check has already told you which fixers are needed. The diff
after running fix remains the review surface.

- package.json: new 'fix' script (npm run fix:oxlint && npm run fix:oxfmt)
- project-specs.md: updated the FIX section to document the new
  aggregator, removed the 'no fix aggregator by design' text in
  two places (FIX section and PREFIX CONVENTION section)
- README.md: same updates, plus the Development section header
  changed from 'Format/Fix' to 'Individual fixes' to reflect
  the new hierarchy

README.md

@@ -7,7 +7,7 @@ Pattern matching for TypeScript/ESM environments (F#-style, not regex).
 - **Build:** `npm run build`
 - **Test:** `npm run test`, `npm run test:ci`
 - **Checks:** `npm run check`, `npm run fix`
-- **Format/Fix:** `npm run fix:oxfmt`, `npm run fix:oxlint`
+- **Individual fixes:** `npm run fix:oxfmt`, `npm run fix:oxlint`
 
 ### Tooling
 
@@ -43,7 +43,7 @@ Pattern matching for TypeScript/ESM environments (F#-style, not regex).
 Script names follow a prefix convention that signals _when_ they run:
 
 - `check:*` — read-only verification. Aggregated by `npm run check`. Used in pre-commit hooks and CI's build job.
-- `fix:*` — mutating counterpart of `check:*`. Run individually (no `npm run fix` aggregator by design — fixes should be intentional, not batched).
+- `fix:*` — mutating counterpart of `check:*`. Aggregated by `npm run fix`. Use after `npm run check` to auto-resolve issues.
 - `test:*` — test scripts. `npm run test` runs the full suite; `test:unit` / `test:ci` are scope-specific variants.
 - `publish:*` — runs only at publish time, in the CI `publish` job (immediately before `npm publish`). There is no local `npm run publish` script — publishing is CI-only by policy.