Feature request: per-file rule ignore in `react-doctor.config.json`

[thinkbig1979]

Summary

ignore.files is currently all-or-nothing: any file matched by a glob has every rule suppressed. There's no way to say "ignore rule X for files matching glob Y while keeping all other rules active." The result is that legitimate file-level exemptions force overshooting — losing coverage for unrelated rules.

(This is distinct from #86, which is a bug about ignore.files not matching at all. This request is for a config-shape extension assuming #86 is fixed.)

Current shape

{
  "ignore": {
    "rules": ["react-doctor/prefer-useReducer"],
    "files": ["app/(dev)/**", "components/modules/diff/**"]
  }
}

Requested shape

{
  "ignore": {
    "rules": ["react-doctor/prefer-useReducer"],
    "files": ["app/(dev)/**"],
    "filesByRule": [
      {
        "files": ["components/modules/diff/**"],
        "rules": ["react-doctor/no-array-index-as-key", "react-doctor/no-render-in-render"]
      },
      {
        "files": ["components/search/HighlightedSnippet.tsx"],
        "rules": ["react/no-danger"]
      }
    ]
  }
}

Concrete cases from one cleanup

File / glob	Rules legitimately suppressed	Other rules we'd like to keep enforced
components/modules/diff/**	no-array-index-as-key (diff segments have no item identity), no-render-in-render (extracted render helpers are local to this single file)	js-combine-iterations, prefer-useReducer, no-effect-event-handler, etc.
components/ai-assistant/AIMessage.tsx	no-array-index-as-key (markdown lines parsed once from immutable message content)	every other react-doctor rule
components/search/HighlightedSnippet.tsx	react/no-danger (file's sole purpose is rendering pre-escaped HTML)	every other rule
**/*PresetList*	no-array-index-as-key for skeleton placeholder lists	the rest

In every row, the current ignore.files shape forces us to disable react-doctor entirely for the file. That regresses coverage for any future violation we'd actually want to know about.

Workarounds today

1. Per-site inline suppressions — works but verbose at scale (e.g. 10 sites in one diff file)
2. Whole-file ignore.files entry — what we've been doing; loses coverage for unrelated rules
3. Helper-component extraction with the helper isolated to its own file — works for the dangerouslySetInnerHTML case but adds files

Suggested implementation

filesByRule (or whatever the name) is a list of { files, rules } pairs. Each pair operates as "for files matching files, disable rules in rules." Rules disabled here do not affect non-matching files; rules disabled in ignore.rules still apply globally.

Repro environment

• react-doctor 0.0.47

Related

• Issue with ignoring files or folders #86 — ignore.files glob matching is broken
• Support enabling only react-doctor-* custom rules #109 — Selective rule enabling (related-but-different)