feat: add request/response dump support to aibridgeproxyd (#24837)

Closes https://github.com/coder/coder/issues/24335

cli/testdata/coder_server_--help.golden

@@ -174,6 +174,12 @@ AI BRIDGE OPTIONS:
           exporting these records to external SIEM or observability systems.
 
 AI BRIDGE PROXY OPTIONS: 
+      --aibridge-proxy-dump-dir string, $CODER_AIBRIDGE_PROXY_DUMP_DIR
+          Directory for dumping MITM request/response pairs to disk for
+          debugging. When set, each proxied request produces .req.txt and
+          .resp.txt files organized by provider. Sensitive headers are redacted.
+          Leave empty to disable.
+
       --aibridge-proxy-allowed-private-cidrs string-array, $CODER_AIBRIDGE_PROXY_ALLOWED_PRIVATE_CIDRS
           Comma-separated list of CIDR ranges that are permitted even though
           they fall within blocked private/reserved IP ranges. By default all

cli/testdata/server-config.yaml.golden

@@ -882,6 +882,11 @@ aibridgeproxy:
   # networks.
   # (default: <unset>, type: string-array)
   allowed_private_cidrs: []
+  # Directory for dumping MITM request/response pairs to disk for debugging. When
+  # set, each proxied request produces .req.txt and .resp.txt files organized by
+  # provider. Sensitive headers are redacted. Leave empty to disable.
+  # (default: <unset>, type: string)
+  api_dump_dir: ""
 # Configure data retention policies for various database tables. Retention
 # policies automatically purge old data to reduce database size and improve
 # performance. Setting a retention duration to 0 disables automatic purging for