feat(miner-manage): CoC-compliant rejection message templates

[JSONbored]

Once a PR is closed/rejected, if the miner needs to leave a single, final, human-readable local note (e.g. in a run summary file or CLI output — NOT necessarily posted anywhere, since posting is a separate write action), it must be courteous, non-defensive, and never re-litigate the maintainer's decision. This issue is pure content/formatting: template strings + a renderer, no GitHub calls.

Deliverables

• packages/gittensory-miner/src/manage/rejection-templates.ts — a small set of message templates keyed by rejection reason bucket (e.g. gate_close, maintainer_close_no_reason, superseded_by_duplicate)
• Templates are static/deterministic strings with placeholders only (no LLM call) — pure string formatting
• Every template reviewed against the project's public-safe-comment rules (no private scoring/reward language) — reuse sanitizePublicComment-style filtering if applicable
• Unit tests: every template renders for every reason bucket with no unresolved placeholders, and none contain banned private-language tokens

References

• src/github/commands.ts (sanitizePublicComment) — the existing public-safe text filter this content should be compatible with
• packages/gittensory-miner/src/manage/rejection-state-machine.ts (new, from the state-machine issue) — the bucket this templates off of
• New: packages/gittensory-miner/src/manage/rejection-templates.ts

[linear-code]

JSO-2421