feat: VersionGuard — newer-major sidecars are read-only with one warning (F5 SLICE-2, INV-16/PUC-4, #14)

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

src/proposalController.ts

@@ -15,6 +15,7 @@ import { emptyArtifact, type Artifact, type Fingerprint, type Proposal, type Pro
 import { resolve, shift, type OffsetRange } from "./anchorer";
 import { addProposal, proposalBody, removeProposal } from "./proposalModel";
 import type { AttributionController } from "./attributionController";
+import type { VersionGuard } from "./versionGuard";
 
 /** Test-facing snapshot of what is currently rendered for a document. */
 export interface RenderedProposal {
@@ -53,6 +54,7 @@ export class ProposalController implements vscode.Disposable {
     private readonly store: CoauthorStore,
     private readonly attribution: AttributionController,
     private readonly rootDir: string,
+    private readonly guard: VersionGuard,
   ) {
     // No commentingRangeProvider: humans never open proposal threads by hand —
     // proposals are born of machine turns only (INV-12 keeps decisions human).
@@ -103,6 +105,7 @@ export class ProposalController implements vscode.Disposable {
     opts?: { turnId?: string; instruction?: string },
   ): Promise<string | undefined> {
     if (!this.isTracked(document)) return undefined;
+    if (this.guard.isReadOnly(this.docPathOf(document.uri))) return undefined;
     const docPath = this.docPathOf(document.uri);
     let proposalId: string | undefined;
     this.store.update(docPath, (a) => {
@@ -137,6 +140,7 @@ export class ProposalController implements vscode.Disposable {
   }
 
   private async accept(state: DocState, proposal: Proposal): Promise<boolean> {
+    if (this.guard.isReadOnly(state.docPath)) return false;
     const document = this.openDoc(state);
     if (!document) return false;
     // INV-11: the fingerprint-guard — exact re-resolve at decision time.
@@ -167,6 +171,7 @@ export class ProposalController implements vscode.Disposable {
   }
 
   private reject(state: DocState, proposal: Proposal): void {
+    if (this.guard.isReadOnly(state.docPath)) return;
     this.store.update(state.docPath, (a) => removeProposal(a, proposal.id));
     const document = this.openDoc(state);
     if (document) this.renderAll(document);