refactor(acr): ACR Store 1 as a disposable memo, not a durable side-store (#305)

The shipped Store 1 persisted repo-file descriptors in a new SqliteObservationStore
— a second, unsynchronized SQLite writer on the event-log DB (no WAL/busy_timeout,
one shared Connection across coroutines) holding a fact the log already carries. That
violates "the event log is the only source of truth" (inv #1/#8): an Observation is
just FileWrittenEvent.path + postImageHash + describe(bytes).render(), and render is a
pure function of content-addressed CAS bytes.

Replace the whole durable apparatus with an in-process memo (descriptorMemo, keyed on
repoRoot+path+contentHash) on the orchestrator, next to the existing artifactContentCache.
Rebuilt from the log on restart, disposable, no external store. Preserves the perf win
(skip CAS read + regex on repeat describes) with none of the concurrency/lock risk.

Deletes: ObservationStore/InMemoryObservationStore/SqliteObservationStore (+ tests),
InfrastructureModule.createObservationStore, the FileReadTool priming path (which never
hit anyway — it keyed on a workspace-relative path while every consumer looks up the
absolute FileWrittenEvent.path), the FileReadConfig/SessionOrchestrator plumbing, and
five orphaned build.gradle deps.

Store 2 (soft-confidence hints) unchanged — it was correct.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HMbPmZZjcXhR2crU82zZ8S

apps/server/src/main/kotlin/com/correx/apps/server/Main.kt

@@ -344,12 +344,9 @@ fun main() {
         ),
     )
 
-    val observationStore = InfrastructureModule.createObservationStore()
     val wsToolRegistryProvider = WorkspaceToolRegistryProvider { workspace ->
         val wsRegistry = InfrastructureModule.createToolRegistry(
-            buildToolConfigForWorkspace(
-                workspace, shellAllowedExecutables, toolsConfig, researchToolConfig, observationStore,
-            ),
+            buildToolConfigForWorkspace(workspace, shellAllowedExecutables, toolsConfig, researchToolConfig),
             extraTools = extraTools,
         )
         val wsExecutor = DispatchingToolExecutor(wsRegistry)
@@ -499,7 +496,6 @@ fun main() {
         compactionService = journalCompactionService,
         artifactKindRegistry = artifactKindRegistry,
         repoKnowledgeRetriever = repoKnowledgeRetriever,
-        observationStore = observationStore,
         readyTaskCounter = com.correx.apps.server.tasks.ProjectReadyTaskCounter(taskService),
         taskClaimCoordinator = com.correx.apps.server.tasks.DefaultTaskClaimCoordinator(
             taskService,
@@ -965,7 +961,6 @@ private fun buildToolConfigForWorkspace(
     shellAllowedExecutables: Set<String>,
     toolsConfig: com.correx.core.config.ToolsConfig,
     research: com.correx.infrastructure.tools.ResearchToolConfig,
-    observationStore: com.correx.core.context.observation.ObservationStore? = null,
 ): ToolConfig = ToolConfig(
     research = research,
     shell = ShellConfig(
@@ -977,8 +972,6 @@ private fun buildToolConfigForWorkspace(
         enabled = toolsConfig.fileReadEnabled,
         allowedPaths = workspace.allowedPaths,
         workingDir = workspace.workingDir,
-        observationStore = observationStore,
-        repoRoot = workspace.workingDir?.toString(),
     ),
     fileWrite = FileWriteConfig(
         enabled = toolsConfig.fileWriteEnabled,