feat: mount user repo as read-only with writable shannon overlay (#273)

* feat: mount user repo as read-only with deliverables bind-mount overlay

* feat: add playground and .playwright-cli overlay mounts

* feat: add filesystem context to pipeline-testing prompts

* fix: use explicit REPO_PATH in filesystem prompt for clarity

* fix: update filesystem prompts with playground notes and absolute screenshot paths

* feat: namespace writable overlays under .shannon/ to avoid polluting host repo

* refactor: rename playground to scratchpad

* fix: redirect playwright-cli output to writable .shannon/ overlay

* fix: pre-create .shannon/ overlay mount points for Linux compatibility

* fix: exclude nested node_modules and dist from Docker build context

* fix: enforce LF line endings for shell scripts on Windows

apps/worker/src/ai/claude-executor.ts

@@ -72,7 +72,7 @@ async function writeErrorLog(
       },
       duration,
     };
-    const logPath = path.join(sourceDir, 'error.log');
+    const logPath = path.join(sourceDir, '.shannon', 'deliverables', 'error.log');
     await fs.appendFile(logPath, `${JSON.stringify(errorLog)}\n`);
   } catch {
     // Best-effort error log writing - don't propagate failures
@@ -152,6 +152,7 @@ export async function runClaudePrompt(
   // 3. Build env vars to pass to SDK subprocesses
   const sdkEnv: Record<string, string> = {
     CLAUDE_CODE_MAX_OUTPUT_TOKENS: process.env.CLAUDE_CODE_MAX_OUTPUT_TOKENS || '64000',
+    PLAYWRIGHT_MCP_OUTPUT_DIR: path.join(sourceDir, '.shannon', '.playwright-cli'),
   };
   const passthroughVars = [
     'ANTHROPIC_API_KEY',