feat(notifications): per-repo summary section for the maintainer recap

[JSONbored]

Digest content section (#1963 'per-repo summary'): a compact per-repo breakdown of PRs reviewed / merged / closed in the recap window, sorted by volume and capped like the alerts embed (MAX_LISTED = 8 at src/review/alerts.ts:150). Pure function over the RecapReport built by the builder bounty; contributes one section to the formatter.

Deliverables

• buildPerRepoRecapSection(report): a sorted, capped list of {repo, reviewed, merged, closed} with a '(+N more)' remainder line matching listSuffix at src/review/alerts.ts:158
• Redact each repo label via the shared redaction primitive (src/signals/redaction.ts) before emitting
• Unit test: sort order, the cap + remainder line (both the <=8 and >8 branches), and a zero-activity repo excluded

References

• src/review/alerts.ts:150
• src/review/alerts.ts:158
• src/signals/redaction.ts:45

Part of #1963.

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size: S · held for later release (gittensor:feature once activated)

[linear-code]

JSO-2342