feat(build): every running build knows its repository — die laufenden Builds und das Worktree-Aufräumen unterscheiden Repositories

Der letzte Übertrag aus Sitzung C: `RunningBuild` trug kein Repository, der
Executor ist aber instanzweit. Zwei Folgen, beide gemessen und jetzt behoben:

- Das Worktree-Aufräumen schützte die Worktrees ALLER Repositories. Ein
  laufender Build eines anderen Repositories auf einem gleichnamigen Branch
  hielt hier einen Worktree fest, dessen Branch längst von origin weg war.
- Die Current-Builds-Ansicht und `/api/builds/current` zeigten die Builds
  aller Repositories, schlugen ihren Status aber in den Ergebnissen NUR
  dieses Repositories nach — ein fremder Build fiel auf RUNNING zurück und
  zeigte einen Zustand, den niemand aufgezeichnet hat. Dasselbe beim
  Live-Log: der Schlüssel eines fremden Builds wurde beantwortet.

`RunningBuild.repo` ist der `RepoContext` selbst, verglichen wird per
Referenz — der Kontext ist die Identität (ADR 0009), und der Executor hat ihn
in `startBuild` ohnehin zur Hand. Watcher, API und UI filtern damit auf ihr
eigenes Repository.

Drei neue Tests, Gegenprobe per Mutation gezogen: Nimmt man die drei Filter
wieder heraus, fallen genau diese drei und sonst keiner. 493 Tests grün,
ktlint sauber.

Architektur-Skill und Plan (docs/plan/22-multi-repo.md) nachgezogen — die
Aussage „RunningBuild carries no repository" stimmte nicht mehr. Was von
Sitzung D bleibt: die repo-bezogenen Routen und die Oberfläche, die weiterhin
nur `registry.current()` bedienen.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/main/kotlin/de/hoennig/werkator/build/BuildExecutor.kt

@@ -97,6 +97,7 @@ class BuildExecutor(
         val stagingDir = Files.createTempDirectory("werkator-build-")
         val runningBuild =
             RunningBuild(
+                repo = repo,
                 branch = branch,
                 build = build,
                 commit = commit,

src/main/kotlin/de/hoennig/werkator/build/RunningBuild.kt

@@ -1,11 +1,19 @@
 package de.hoennig.werkator.build
 
 import de.hoennig.werkator.config.BuildDefinition
+import de.hoennig.werkator.repo.RepoContext
 import java.nio.file.Path
 import java.time.Instant
 
 /** Handle to a build accepted by the [BuildExecutor]; log paths become valid once the build runs. */
 data class RunningBuild(
+    /**
+     * The repository this build belongs to; the context object is the identity
+     * (ADR 0009), so it compares by reference. Without it neither the current-builds
+     * view nor the watcher's worktree pruning could tell two repositories apart —
+     * both would see every repository's running builds as their own.
+     */
+    val repo: RepoContext,
     /** The git branch being built. */
     val branch: String,
     /** The build definition (job) this build runs; its settings are resolved from config at run time. */

src/main/kotlin/de/hoennig/werkator/server/BuildsApiController.kt

@@ -55,11 +55,17 @@ class BuildsApiController(
 
     private fun BuildResult.isLatestGreen(): Boolean = repository.latestGreenFor(name)?.artifactKey == artifactKey
 
-    /** The currently executing builds — several are possible, up to `executor.maxConcurrent`. */
+    /**
+     * The currently executing builds of the served repository — several are possible,
+     * up to `executor.maxConcurrent`. The executor is instance-global and returns the
+     * builds of every registered repository, so this view filters: its [repository]
+     * holds only this repository's results, and a foreign build looked up in them
+     * would fall back to RUNNING and show a status nobody recorded.
+     */
     @GetMapping("/api/builds/current")
     fun current(): List<CurrentBuildDto> {
         val results = repository.history()
-        return buildExecutor.currentBuilds().map { build ->
+        return buildExecutor.currentBuilds().filter { it.repo === repo }.map { build ->
             CurrentBuildDto(
                 branch = build.branch,
                 name = build.name,
@@ -82,7 +88,7 @@ class BuildsApiController(
         @RequestParam(defaultValue = "0") offset: Long,
     ): ResponseEntity<Any> {
         val build =
-            buildExecutor.currentBuilds().firstOrNull { it.artifactKey == artifactKey }
+            buildExecutor.currentBuilds().firstOrNull { it.repo === repo && it.artifactKey == artifactKey }
                 ?: return notFound("no running build with artifact key '$artifactKey'")
         return ResponseEntity.ok(readLogTail(artifactKey, build.liveLogFile, offset))
     }

src/main/kotlin/de/hoennig/werkator/server/UiController.kt

@@ -106,7 +106,7 @@ class UiController(
         val links = baseModel(model, view = "current", pageTitle = "Current Builds")
         val results = repository.history()
         val currentBuilds =
-            buildExecutor.currentBuilds().map { build ->
+            buildExecutor.currentBuilds().filter { it.repo === repo }.map { build ->
                 CurrentBuildView(
                     branch = build.branch,
                     name = build.name,

src/main/kotlin/de/hoennig/werkator/watcher/Watcher.kt

@@ -506,7 +506,10 @@ class Watcher(
         }
         val keep = originBranches.map { ArtifactKeys.branchKey(it) }.toMutableSet()
         // never delete under a build that is still queued or executing
-        buildExecutor.currentBuilds().forEach { keep += ArtifactKeys.branchKey(it.branch) }
+        buildExecutor
+            .currentBuilds()
+            .filter { it.repo === repo }
+            .forEach { keep += ArtifactKeys.branchKey(it.branch) }
         repo.results
             .latestPerName()
             .filter { it.status == BuildStatus.PENDING || it.status == BuildStatus.RUNNING }