Step 01: Build State Domain and Repository

Prerequisites: none. Read README.md and 00-legacy-analysis.md first.

Goal

A tested domain model for build results plus a persistent repository, replacing the legacy build-results.tsv.

Create package de.hoennig.gittally.build:

BuildStatus enum: PENDING, RUNNING, SUCCESS, FAILED, INTERRUPTED, CANCELLED. Add isTerminal, isRestartable (pending/running/interrupted) properties.
BuildResult data class: branch, commit SHA, status, startedAt, duration, artifactKey. Use java.time.Instant/Duration; format only at the edges.
BuildResultRepository interface: append, update status of latest entry for a branch, query latest per branch, query history, delete entry, prune.
FileBuildResultRepository: JSON file at .git/gittally/build-results.json. Write atomically (write temp file, then Files.move with ATOMIC_MOVE). Reuse the Jackson YAML/JSON setup style from ConfigLoader.

Business logic to include (port from legacy, see analysis):

markStaleRunningAsInterrupted() — called at startup; running → interrupted, superseded pending → interrupted.
Retention pruning: keep N builds per branch (artifacts.retentionPerBranch); drop entries for branches no longer on origin (branch list passed in as a parameter, no git dependency here).

No git access, no Gitea, no execution — pure domain and file I/O.
Artifact directory pruning (step 05 consumes the pruning result).
Age-based retention (legacy supported h/d suffixes); count-based only, extend later if needed.

Uses existing artifacts.retentionPerBranch. No new keys expected.

Kotest FunSpec, no Spring context needed.

Round-trip persistence, atomicity (temp file cleaned up).
Status transition helpers and markStaleRunningAsInterrupted edge cases.
Retention pruning: per-branch count, removed branches, ordering by timestamp.
Corrupt/missing file → empty repository, no crash (legacy failed silently; we log a warning).