feat(acr): Store 2 soft-confidence hints + Store 1 FileReadTool priming (#305)

Store 2 (Fixes): ConceptCompilerProjection already tracked the
unconfirmed(validatedFixes>=1)/falsified(contradicted)/confirmed(promoted)
lifecycle as data, but only confirmed (>=threshold) clusters were ever
delivered. unconfirmedFixEntries reactively matches the CURRENT retry's
classKey against that state and injects a soft one-shot hint (below
threshold) or steer-away (contradicted) before hard promotion — wired
into stage context build in SessionOrchestratorExecution.kt.

Store 3 (Plan-shapes): already shipped as SessionOrchestratorPlanPatterns.kt
(deterministic keyword-Jaccard over eventStore.allEvents(), no embedder
needed) — confirmed complete, no new code required.

FileReadTool hot-path extension to Store 1: a whole-file read now primes
the cross-session ObservationStore (when wired) the same way the write
path already does, so a later describeCached lookup for the same content
hash is warm even if the file was only read, not written, this session.

infrastructure/tools/src/main/kotlin/com/correx/infrastructure/tools/ToolConfig.kt

@@ -1,5 +1,6 @@
 package com.correx.infrastructure.tools
 
+import com.correx.core.context.observation.ObservationStore
 import com.correx.core.tools.contract.Tool
 import com.correx.infrastructure.tools.filesystem.FileDeleteTool
 import com.correx.infrastructure.tools.filesystem.FileEditTool
@@ -39,6 +40,9 @@ data class FileReadConfig(
     val enabled: Boolean = false,
     val allowedPaths: Set<Path> = emptySet(),
     val workingDir: Path? = null,
+    // ACR Store 1 hot-path priming (docs/plans/2026-07-21-acr-knowledge-accretion.md); both null is a no-op.
+    val observationStore: ObservationStore? = null,
+    val repoRoot: String? = null,
 )
 data class FileWriteConfig(
     val enabled: Boolean = false,
@@ -75,6 +79,8 @@ fun ToolConfig.buildTools(): List<Tool> = buildList {
             FileReadTool(
                 allowedPaths = fileRead.allowedPaths,
                 workingDir = fileRead.workingDir,
+                observationStore = fileRead.observationStore,
+                repoRoot = fileRead.repoRoot,
             ),
         )
         // list_dir is read-only enumeration; shares the reader's jail + anchor and the same toggle.