feat: propose safe rules from corrections

[tcballard]

What changed

• make one-off manual correction independent from ruleset changes
• generate one local, structured correction-rule proposal after the file is safely filed
• show the inference evidence and exact editable rule before any activation
• reuse the Issue feat(rules): preview filing outcomes before activation #41 preview against the corrected file or up to eight selected files
• detect duplicates, same-subject conflicts, broader/narrower overlaps, invalid routes, ordering problems, and catch-all conflicts
• insert an approved specific rule immediately before the catch-all while preserving every unrelated rule
• record accepted, edited, discarded, and pending proposal outcomes in the local Activity ledger
• retry invalid Foundation Models proposals within a bounded loop while keeping Swift validation authoritative

Product impact

Correcting a file no longer risks silently teaching the hat. The correction completes first. A reusable rule is then an optional, inspectable proposal that can be edited, previewed, explicitly added, or discarded without affecting the already-filed item.

File content used for the proposal stays in the on-device Foundation Models path. No correction, excerpt, or teaching history is uploaded solely to learn a rule.

Validation

• focused correction/ruleset suite: 6 tests passed
• GitHub CI full suite: passed in 3m17s
• package app build: passed
• no-signing Xcode build including app, Finder extension, and Sparkle: passed
• XcodeGen reproducibility check: passed
• native visual and accessibility pass: correction disclosure, loading, generated proposal, overlap warning, editable rule, Preview menu, Add Rule, and Escape-to-discard inspected
• isolated real-model pass: unsupported placeholders were refused, bounded retry produced a validated proposal, overlap was explained, and discard left the saved rules byte-for-byte unchanged
• local full suite: 91 of 94 tests passed; the three unchanged Vision OCR fixtures failed on this Mac with TextRecognition.CRImageReaderError error 1, while all 94 passed on the fresh GitHub runner

Closes #39