chore(bin/up): DEBUG=1 writes LLM debug logs to /app/logging (host: logging/)

Add a DEBUG=1 convenience flag to bin/up that turns on full LLM debug logging
(DISPATCH_DEBUG_LLM) plus the per-step usage/cache split (DISPATCH_DEBUG_USAGE)
and routes the JSON request/response files into the container's /app/logging,
which maps to the project-root logging/ dir on the host via the existing .:/app
bind mount. This makes it easy to verify cache hits (including the prompt-cache
warming replay) without docker exec.

- bin/up: DEBUG=1 sets DISPATCH_DEBUG_LLM/_USAGE=1 and DISPATCH_DEBUG_LLM_DIR=
  /app/logging as DEFAULTS (explicit DISPATCH_DEBUG_* still win). Pre-creates
  the host log dir; /app/* targets are already host-owned so no sudo chown,
  while the /tmp fallback keeps its ownership fix.
- docker-compose.yml: forward DISPATCH_DEBUG_LLM_DIR into the api container.
- .gitignore: ignore logging/.

1 files changed, 5 insertions, 0 deletions

diff --git a/docker-compose.yml b/docker-compose.yml
index aedd0f2..4dd914d 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -28,6 +28,11 @@ services:
       DISPATCH_DEBUG_LLM: ${DISPATCH_DEBUG_LLM:-}
       DISPATCH_DEBUG_LLM_VERBOSITY: ${DISPATCH_DEBUG_LLM_VERBOSITY:-}
       DISPATCH_DEBUG_USAGE: ${DISPATCH_DEBUG_USAGE:-}
+      # Where the debug logger writes its JSON files INSIDE the container.
+      # `DEBUG=1 bin/up` sets this to /app/logging, which maps to the
+      # gitignored `logging/` dir on the host via the `.:/app` bind mount.
+      # Empty ⇒ the logger falls back to /tmp/dispatch/llm-debug.
+      DISPATCH_DEBUG_LLM_DIR: ${DISPATCH_DEBUG_LLM_DIR:-}
 
   frontend:
     build: