feat(dc_bridge): extract the Uploader into its own dc_uploader process

[Minipada]

Summary

Closes #446

• The Uploader (ADR-0005) is no longer a worker thread inside dc_bridge. It is now dc_uploader, a standalone executable in the dc_bridge colcon package, configured entirely by DC_UPLOADER_* environment variables with no ROS dependency — no rclcpp, no ROS params.
• dc_bridge keeps only the Files subscription and the durable intent-queue write side (ADR-0005/DC 2.0: durable Uploader intent queue — File uploads survive Bridge restarts #265); it no longer links the AWS SDK at all.
• IntentQueue gains rescan(): the queue's on-disk format was already crash-atomic and multi-process-safe, but each process's in-memory scheduling state previously only ever loaded from disk once, at construction. A separate dc_uploader process holding its own IntentQueue instance over the same directory needed a way to learn about intents the Bridge process enqueues after that — rescan() is that mechanism, polled every cycle.
• dc_bringup.launch.py starts dc_uploader automatically alongside dc_bridge (same ExecuteProcess pattern already used for dc_mcap_writer) whenever a receives: files Destination is configured, translating that Destination plus files.*/uploader.data_dir into dc_uploader's environment — so every existing params file (tools/e2e/params/*.yaml, the demo params, etc.) keeps working unchanged.
• New ADR: docs/adr/0014-uploader-runs-as-its-own-process.md.

Acceptance criteria from #446:

• The Uploader runs as a standalone process, not inside the Bridge
• Configured entirely by environment variables (queue path, files path, object-storage endpoint and credentials)
• No ROS dependency
• Emits each File's metadata Record over the shipper ingest protocol
• The Bridge still owns the Files subscription and still writes upload intents
• Killing the Uploader mid-upload loses nothing: pending intents replay on restart (unchanged IntentQueue crash-replay guarantee, exercised per-process via rescan())
• Killing the Uploader does not affect Record collection (no shared address space left — the Bridge never blocks on or depends on dc_uploader)
• The zero-loss E2E harness still reports zero loss, including File uploads (unchanged at the container level — dc_uploader now runs inside the same container alongside dc_bridge, both launched by the existing dc_bringup.launch.py)

Still one machine at this point (per the issue) — containerizing dc_uploader into its own image/container is #447's work, not this change's.

Test plan

• Full tools/e2e/scripts/build.sh run: colcon build + colcon test — 656 tests, 0 errors, 0 failures, 0 skipped.
• prek run --all-files --skip build-doc — all hooks pass (clang-format, ruff, REUSE/SPDX, etc.).
• Manual smoke test: ran dc_uploader in the built container against live RustFS with DC_UPLOADER_* env vars set — started, connected, and shut down cleanly on SIGTERM.
• Manual error-path check: ran dc_uploader with no env vars — fails fast with a clear "required environment variable ... is not set" message instead of a crash.
• New unit tests: process_config_test.cpp (env-var parsing/validation) and new IntentQueue rescan tests in intent_queue_test.cpp.

🤖 Generated with Claude Code

https://claude.ai/code/session_01VXhyy2nX5JokxtTnGdwzjy

[codecov]

Codecov Report

❌ Patch coverage is 52.55814% with 102 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.43%. Comparing base (393b4f0) to head (1ea6275).

Files with missing lines	Patch %	Lines
dc_bridge/src/uploader_main.cpp	0.00%	93 Missing ⚠️
dc_bridge/src/uploader/intent_queue.cpp	90.25%	4 Missing ⚠️
dc_bridge/src/uploader/process_config.cpp	94.94%	4 Missing ⚠️
dc_bridge/src/bridge_node.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            jazzy     #459      +/-   ##
==========================================
+ Coverage   71.00%   71.43%   +0.43%     
==========================================
  Files         120      123       +3     
  Lines        7462     7553      +91     
==========================================
+ Hits         5298     5395      +97     
+ Misses       2164     2158       -6     

Flag	Coverage Δ
cpp-jazzy	71.43% <52.56%> (+0.43%)	⬆️

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