Removing a self-correction leaves the comma that closed it: "Send the file to Sam, before lunch."

## What happens

When the recogniser punctuates a correction as a parenthetical, `SelfCorrectionPass` removes the discarded half and the trigger but keeps the comma after the replacement, which now separates nothing.

From `uttrflow-dev bench` on main (synthetic `say` clips from `Scripts/dictation_bench.py`, both the shipping route and rules only, identical):

| Clip (the corpus names are replaced here) | Recogniser | Inserted |
|---|---|---|
| `selfcorrection1-daniel` | `Send the file to Alex, I mean to Sam, before lunch.` | `Send the file to Sam, before lunch.` |
| `selfcorrection3-samantha` | `Book a table for six, actually eight, at the usual place.` | `Book a table for eight, at the usual place.` |

Reproducible without audio:

```
.build/release/uttrflow-dev clean --engine rules 'Send the file to Alex, I mean to Sam, before lunch.'
```

The bench's word error rate cannot see it (it drops punctuation), so the category reports 0.0% final.

## Why it matters

Two of the four self-correction clips in the bench corpus come out with a stray comma. It is small, but it is on every correction spoken with a pause on both sides, which is how people usually say them.

## Acceptance criteria

- When the discarded span began after a comma (or the trigger was set off by commas), the comma that closes the replacement is removed too, unless the sentence needs it (for example before a following clause that already had one).
- Tests in `Tests/UttrflowAITests/Passes/SelfCorrectionPassTests.swift` for both clips above.
- A corpus case with the comma form, listed in `RulesCorpusTests.rulesMustPass`.

Start with SelfCorrectionPass and its tests in Tests/UttrflowAITests/Passes/SelfCorrectionPassTests.swift, then run the reproducible clean command from the issue. Add coverage for both shown corrections and a comma-form corpus case in RulesCorpusTests.rulesMustPass. Done means the replacement-closing comma is removed when it is stray, while required sentence punctuation remains.

Written by the indexing model from the issue text.