feat(docker): harden session mode + File Viewer button (v1.4.1)

Docker cases: seamless Claude auth (seed ~/.claude.json instead of the
corruption-prone single-file mount), full credential-store isolation for
claude + codex/gemini/gcloud/opencode (share only transcripts/rollouts,
seed the rest), auto-build the base image on first use, C.UTF-8 locale
(fixes box-drawing), collapsed/shortened Create-Case UI + short "(docker)"
case-menu tags, and w<n>-<case> tab naming for docker/remote sessions.
Also: opt-in File Viewer header button; fix a TZ-boundary flaky test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/web/sse-events.ts

@@ -377,6 +377,14 @@ export const DockerExportComplete = 'docker:exportComplete' as const;
 export const DockerExportFailed = 'docker:exportFailed' as const;
 /** A docker bundle was imported into a new case. */
 export const DockerImportComplete = 'docker:importComplete' as const;
+/** The agent base image started building (first Docker case; auto-build on first use). */
+export const DockerImageBuildStarted = 'docker:imageBuildStarted' as const;
+/** A line of agent base-image build output (progress surfacing). */
+export const DockerImageBuildProgress = 'docker:imageBuildProgress' as const;
+/** The agent base image finished building successfully. */
+export const DockerImageBuildComplete = 'docker:imageBuildComplete' as const;
+/** The agent base image build failed. */
+export const DockerImageBuildFailed = 'docker:imageBuildFailed' as const;
 
 // ─── Namespace Re-export ─────────────────────────────────────────────────────
 
@@ -564,4 +572,8 @@ export const SseEvent = {
   DockerExportComplete,
   DockerExportFailed,
   DockerImportComplete,
+  DockerImageBuildStarted,
+  DockerImageBuildProgress,
+  DockerImageBuildComplete,
+  DockerImageBuildFailed,
 } as const;