Update rosbag_blackbox README to reflect current implementation

[Copilot]

The README was written against an earlier version of the package and omitted several significant features added since, while also containing incorrect default values.

Corrections

• Default buffer_duration: 10s → 60s (Features table, Node Parameters, Launch File)
• Default snapshot_name_pattern: snapshot_{datetime} → snapshot_{trigger}_{datetime}

Missing features documented

• Type-based topic matching (type: "sensor_msgs/msg/Image") and combined pattern + type rules
• Auto-snapshot (auto_snapshot: config section, sliding-window behaviour)
• Node parameter snapshotting (node_params: config section, node_params.yaml sidecar)
• Sensor visualisation endpoints: LaserScan → top-view PNG, Odometry → trajectory PNG, OccupancyGrid → map PNG
• Topic statistics endpoint (/topic_stats/{topic})
• /rosout log querying with level/node/grep filters

REST endpoint table

Added the 5 missing endpoints; corrected image endpoint response format (returns JSON {"data_url": "data:image/png;base64,…"}, not a raw PNG byte stream). Added query-parameter tables for /rosout, image/sensor, and trajectory endpoints.

MCP Tools section rewritten

The old section listed hand-crafted tool names (list_snapshots, select_snapshot, search_topics, …) that never existed. Tools are auto-derived from FastAPI routes via FastMCP.from_fastapi; the section now lists the actual function-derived names (list_snapshots_rest, get_metadata_rest, get_rosout_rest, etc.) and shows a corrected example interaction.

Configuration Reference restructured

Split into subsections (Buffer Settings, Snapshot Output, Automatic Snapshots, Node Parameter Snapshotting, Topic Recording Rules) and updated all examples to match defaults in the code.

Architecture diagram

Updated to show the auto-snapshot timer, node_params.yaml write path, and the full set of REST endpoints served by snapshot_server.

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