feat(playground): add debug tracing and inline source specifier support

Author: Michael Lin

README.md

@@ -196,6 +196,8 @@ pnpm cli -- render-plan examples/runtime/counter-plan.json
 
 # Browser playground
 pnpm playground
+pnpm cli -- playground --debug
+RENDERIFY_PLAYGROUND_DEBUG=1 pnpm playground
 
 # Optional security env
 RENDERIFY_SECURITY_PROFILE=strict pnpm playground
@@ -223,6 +225,8 @@ RENDERIFY_RUNTIME_BROWSER_SANDBOX_FAIL_CLOSED=true pnpm playground
 RENDERIFY_LLM_USE_STRUCTURED_OUTPUT=false pnpm playground
 ```
 
+When debug mode is enabled, playground logs key inbound/outbound request summaries and exposes `GET /api/debug/stats` for request distribution diagnostics.
+
 ### Playground Hash Deep-Link
 
 The playground can auto-render from URL hash payloads:

packages/cli/README.md

@@ -29,7 +29,7 @@ renderify run <prompt>          # Render prompt and print HTML
 renderify plan <prompt>         # Print RuntimePlan JSON
 renderify probe-plan <file>     # Probe plan dependencies and policy compatibility
 renderify render-plan <file>    # Execute RuntimePlan JSON file and print HTML
-renderify playground [port]     # Start browser playground server
+renderify playground [port] [--debug]  # Start browser playground server
 ```
 
 ## Quick Start
@@ -53,6 +53,9 @@ renderify render-plan ./examples/runtime/recharts-dashboard-plan.json
 - `RENDERIFY_LLM_MODEL`
 - `RENDERIFY_LLM_BASE_URL`
 - `RENDERIFY_SECURITY_PROFILE` (`strict`, `balanced`, `relaxed`)
+- `RENDERIFY_PLAYGROUND_DEBUG` (`1`, `true`, `yes`, `on`)
+
+When debug mode is enabled, playground prints key inbound/outbound request logs and exposes `/api/debug/stats` for request distribution snapshots.
 
 See `../../docs/getting-started.md` and `../../docs/security.md` for runtime and policy options.