#28164 fix(agent-pane): carry workflow progress tray and inspector

Carry-forward of orphan #27886, rebased onto current feat-cmux-next after resolving its conflict with the base.

Running workflows now show completed/started agent counts, failed and queued agents, and token usage in the default running tray and Session Info inspector. Existing action text remains, with progress beneath it so long names do not crowd out counts. The refresh key includes usage and progress fields so successive updates re-render.

The original commits and authorship are preserved via cherry-pick: c2750629a5c and a68fd2cadbe.

Validation: webviews/test/subagent-tray.test.tsx covers tray and inspector updates, missing/zero progress, and unrelated-row preservation. Fleet checks pending.

Gallery: agent-pane.subagent-tray/workflow-progress
Gallery / captures: agent-pane.subagent-tray/workflow-progress; before/after media-tour labels requested from ux-owner.

Risk: row height increases only when progress exists; existing action, open, Stop, and spinner behavior remain unchanged. No timer or observer is added.

Closes orphan #27886 after this replacement lands.

Agent session: agent session

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Summary by cubic

Carry-forward of orphan #27886, rebased onto feat-cmux-next.

Running workflows now show completed/started agent counts, failed and queued agents, and token usage in the default running tray and Session Info inspector. Progress appears beneath the existing action text so long names don't crowd out the counts.

• Progress appears only when counts or usage exist, so rows without progress keep their current height and behavior.
• The refresh key includes usage and progress fields, so successive updates re-render.
• Tests in webviews/test/subagent-tray.test.tsx cover tray and inspector updates, missing or zero progress, and preservation of unrelated rows.

Closes orphan #27886.