bug(desktop): collapsed tool rows show no invocation target — ordinary tool cards read empty

[me2seeks]

Symptom

In the Desktop transcript, an ordinary collapsed tool row and collapsed group header can have no invocation target during the live window. A row may read ● Bash instead of ● Bash $ git status --porcelain, so the user cannot tell what a long-running call is doing.

After durable args are available, the shared invocation formatter can derive a command, path, pattern, title, or URL. The remaining cross-surface gap is that Runtime Host live tool_start frames intentionally omit full args, while Desktop's collapsed target previously depended primarily on intent.

Scope

This issue covers the ordinary-tool collapsed-row what slot:

• carry a bounded, redacted invocation preview through the live Runtime Host event;
• render intent ?? invocation preview in the single-call row and group header;
• keep durable args/history as the full-data authority;
• preserve the existing expanded detail panel and result deduplication.

Scope split

Task Ledger tools are not ordinary invocation summaries. task_create needs committed IDs and the complete created set; task_update needs the subject and mutation snapshot owned by the Session Task Ledger. Their semantic timeline is tracked separately in #4179 and is intentionally excluded from this issue and #3376.

Acceptance

• An ordinary tool with a safe structured target shows one line describing what it is doing in the collapsed row and collapsed group header during the live window.
• Preview data is allowlist-shaped, bounded, and redacted; full file bodies and arbitrary provider/MCP payloads do not enter the live wire.
• A settled or historical row continues to use durable args.
• Tools without a safe preview keep the current name-only fallback.
• Task Ledger presentation remains unchanged and is handled by feat(runtime-host,cli): render Task Ledger mutations as a durable semantic timeline #4179.

[me2seeks]

Cross-check on "does this reproduce everywhere": Not environment-specific — the empty collapsed row is fully determined by shared rendering code (packages/ui/src/tool-activity.tsx), not by machine or install; git history shows the intent-only target line has been there since #1254 and survived the Astryx migration (#1728). A work desktop running this codebase reproduces it identically.

Correction to an earlier version of this comment: I initially claimed the TUI already renders the invocation target and only Desktop lacks it. That was wrong — quiet Bash calls in the TUI compact row also show no command (● Bash (no output)); the command sits in args but the row doesn't render it. Same symptom, two surfaces, two formatters. TUI side is tracked in #3338.

[me2seeks]

TUI/CLI counterpart: #3338 (compact-row no output for quiet Bash + task_* JSON dump).

[me2seeks]

Claiming this one — I'm working on the fix.