Task: Android storage metrics device verification

[ryo100794]

Problem

Static storage metric checks now exist, but device behavior still needs validation after real build, prune, rebuild, and container edit/copy-up flows. UI totals must not double-count shared layer data.

Scope

• Verify layer store, image-view, container-private, total, free-space, volume, and build-cache metrics on device.
• Confirm shared layer-pool accounting is nonnegative and not double-counted as image unique storage.
• Validate metric refresh after build, prune, rebuild, and container file edit/copy-up.

Non-goals

• Do not move file contents into SQLite/DB storage.
• Do not claim exact overlayfs inode semantics.

Acceptance checks

• python3 scripts/verify-storage-metrics.py passes for fixture/static coverage.
• Device/manual or smoke evidence captures /system/df, /images/json, and /containers/json?all=1&size=1 around build/prune/rebuild/edit flows.
• Docs/test artifact records the result and any remaining gap.

Current context

• Static lane: scripts/verify-storage-metrics.py.
• Docs: docs/test/STORAGE_METRICS.md, docs/design/COW_OVERLAY_STORAGE.md.
• TODO: Android storage metrics verification entry.

[ryo100794]

Agent implementation update for #7.

Changed files:

• scripts/verify-storage-metrics.py
• docs/test/STORAGE_METRICS.md
• tests/storage_metrics/test_verify_storage_metrics.py
• scripts/android-device-smoke.sh

Implemented:

• --capture-device, --dry-run, --output, ADB/package/socket/timeout options.
• HTTP body parsing and endpoint capture for /system/df, /images/json, and /containers/json?all=1&size=1.
• Dry-run mode that does not execute ADB.
• Focused tests for dry-run, mocked capture, bad JSON, and double-count detection.
• Smoke script adjustment so static checks can see the Engine exec path while preserving bracket argv probe.

Checks run by agent:

• python3 scripts/verify-storage-metrics.py
• python3 scripts/verify-storage-metrics.py --capture-device --dry-run
• python3 -m unittest tests.storage_metrics.test_verify_storage_metrics
• python3 scripts/verify-ui-actions.py

Note: agent saw scripts/verify-fast.sh fail in compat-audit.py on Vulkan ICD compute forwarding, which is outside #7 and is being handled under #4.