Port the adaptive ID length algorithm from SQLite to Dolt backend.
The ID length now scales from 3-8 characters based on database size
using birthday paradox collision probability calculations.
- Add adaptive_length.go with length computation based on issue count
- Update generateIssueID to use adaptive length with nonce fallback
- Add collision detection and retry logic matching SQLite behavior
Fixes bd-c40999
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Executed-By: mayor
Role: mayor
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