wip(freestyle/acr): grounding & edit-tool fixes + ACR-compiler experiment

This branch's uncommitted WIP, committed together (entangled at file level).
Distinct pieces of work:

Freestyle QA fixes (this session):
- FileEditTool: pre-validate replace anchor in validateRequest — reject a
  missing/ambiguous target BEFORE the approval gate, mirroring read/write's
  file-not-found / read-before-write pre-checks. Shared not-found/ambiguous
  messages between validate and execute so they can't drift.
- PlanGrounder: add `scanned` flag; when no RepoMapComputedEvent was recorded,
  repoMapPaths is "unknown" not "empty workspace" — skip scope grounding
  (which proves a path ABSENT) so real paths (apps/server/**) aren't falsely
  rejected. Build-manifest check still runs.
- FreestyleDriver: wire scanned=(repoMap!=null); on plan rejection emit a
  session-terminal WorkflowFailedEvent so a rejected run reads FAILED, not the
  COMPLETED-lie (last verdict was the planning-phase WorkflowCompleted).
- ServerModule: resolve project-memory workspace root from the session's bound
  workspace (sessionWorkspaceRoot) instead of boot-static pm.repoRoot(), fixing
  the workspace-binding divergence (correx vs empty scratch dir). Retire tracked
  in Vikunja #266.
- LaunchRegistrationRaceTest: join registered jobs before asserting launchCount
  — computeIfAbsent returns the Job immediately but the fire-and-forget launch
  body lagged awaitAll (the 49-vs-50 flake).

ACR concept-compiler experiment (pre-existing WIP on this branch):
- ExecutionPlanCompiler/Model/PlanLinter, #264 needs-seam (sessionArtifacts),
  LSP diagnostics subsystem (LspDiagnosticEvents/Runner/Lsp4j), BootWorkspace,
  config surface, workflow prompts/schemas, orchestrator advance-don't-rerun.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/AGENTS.md

@@ -21,6 +21,7 @@ All sources under `apps/server/src/`.
 - `GET /metrics/tool-reliability` — per-model tool-call validity across the event log (`ToolReliabilityInspectionService`); groundwork for capability-aware routing
 - Optional `[git]` transport creates `run/<sessionId>` from a server-local checkout and pushes it at terminal state; clients review with ordinary Git and never supply a remote URL as `cwd`.
 - Repo-map L3 embeddings use bounded, recorded source descriptors (module/package, imports, leading purpose comment, symbols); raw file bodies are never embedded. Their versioned `repomap:v2` namespace forces a one-time re-embed when the semantic document format changes.
+- At boot, `tools.workspace_root` is the authoritative tool jail and project-observation root. A configured `tools.working_dir` may only remain distinct when it is contained by that root; an outside value is clamped to `workspace_root`. Project memory and repo-map indexing are also rebound to `workspace_root`, so a stale `[project].root` cannot inject files from outside the session workspace.
 
 ### WebSocket protocol (`/ws`)
 - **ServerMessage** (server → client): sealed hierarchy — `SessionMessage` (event-derived, carries `sequence` + `sessionSequence`) and `NonEventMessage` (control/infra). Variants include session lifecycle, approval requests, clarification requests, narration, proposed workflows, health/metrics pushes.