Port FixType contract to current Fix common errors rules

[Blackspirits]

Purpose

Current-base audit/port of upstream draft stack PR SubtitleEdit#14442 onto Subtitle Edit c77c4b428649ce7030e6cf218b4d7c384b955232.

The original PR is 628 upstream commits behind and no longer mergeable. This port preserves all current rule changes and adds only the taxonomy contract:

• new FixType enum: Time, Formatting, Dialog, Punctuation, Casing, Spacing, Characters, OCR;
• FixType FixType { get; } on IFixCommonError;
• all 39 libse rules plus UI FixCommonOcrErrors declare a category.

Rebase integrity

Only three rule files changed upstream since SubtitleEdit#14442's base:

• FixHyphensRemoveDashSingleLine.cs
• FixMissingPeriodsAtEndOfLine.cs
• FixShortDisplayTimes.cs

Those three were patched on top of the current versions. All other changed blobs are identical to the original SubtitleEdit#14442 changes because their files did not drift.

Audit notes

The contract is structurally complete for the current 40 implementations. Category assignments are retained from SubtitleEdit#14442 for behavioral comparison; ambiguous taxonomy cases such as FixDoubleGreaterThan can be adjudicated separately without changing execution behavior.

Validation

• current upstream base: c77c4b428649ce7030e6cf218b4d7c384b955232
• final HEAD: cd4ad6454a55651d6b2563fed0babc58b8be9991
• taxonomy review moved FixDoubleGreaterThan from Punctuation to Dialog, matching its behavior as removal of a >> speaker/dialogue marker
• final-head full solution restore passed
• final-head full solution build passed
• final-head full solution test suite passed on the first run
• UI suite: 5,151 passed, 9 skipped, 0 failed (5,160 total)
• retry step was not used
• final validation run: #34787974854
• no merge/promotion intended during audit

AI assistance: ChatGPT was used to rebase the stale contract without overwriting current rule fixes and to audit category coverage.

[Blackspirits]

Independent adversarial re-check: the stale SubtitleEdit#14442 stack was ported onto current c77c4b4 without overwriting later rule changes. The three drifted rule files were patched on top of current content; all remaining changed blobs are unchanged from the original contract addition. Full CI #34787730169 passed restore, build and the complete solution suite on the first run; UITests reported 5,151 passed, 9 skipped and 0 failed. Retry was not used. No structural blocker identified; taxonomy semantics remain under review for ambiguous cases such as FixDoubleGreaterThan. Keep draft; no merge performed.

[Blackspirits]

Final independent re-check: the contract is complete for all current IFixCommonError implementations and preserves the three rule files that drifted upstream after SubtitleEdit#14442. Taxonomy review additionally moved FixDoubleGreaterThan to Dialog because it removes the >> speaker/dialogue marker rather than repairing ordinary punctuation. Final-head CI #34787974854 passed restore, build and the complete solution suite on the first run; UITests reported 5,151 passed, 9 skipped and 0 failed. Retry was not used. No blocker identified. Keep draft; no merge performed.