feat(desktop): polish agent-session transcript UI atop declared-ownership model

[tellaho]

Overview

Category: improvement
User Impact: The agent-session transcript view gets a polish pass — cleaner grouping, tool-call summaries, assistant-bubble avatars, and density-aware markdown — now reconciled with the declared-ownership activity model.

Problem: PR #1061 (tho/activity-ui-polish) drifted 164 commits behind main and was based on a now-closed branch (tho/activity-ingress-ownership, #1060). A straight rebase was gnarly — the branch's own later commits delete what its early commits add. Meanwhile #1229 reworked activity authorization from key-custody to declared ownership, superseding the old ingress foundation.

Solution: Replayed the 20 UI-polish commits as a single net diff onto fresh main, dropping the 3 superseded ingress commits and hand-reconciling against #1229's merged model. The polish layers cleanly atop viewerIsOwner = isCurrentUserOwner || isOwner rather than reverting it.

Supersedes #1061 (whose base branch is closed). Observer-seed screenshot work is intentionally excluded as a separate follow-up.

Reconcile notes

markdown.tsx — ported the compact/tight variant system into main's newer lightbox/spoiler markdown component (rather than overwriting it), layering variant density/leading overrides after the base owl-spacing so tailwind-merge wins. Dropped the branch's hardcoded text-[15px] in favor of main's rem-token text-sm base (post-#1052 zoom-safe scale).

AgentSessionTranscriptList.tsx — preserved #1089's content-visibility-auto on the item wrapper (perf win for long transcripts).

agentSessionTranscript.ts — pass TranscriptItemContext (not channelId).

managed_agents / runtime.rs — threaded avatar_url through ManagedAgentSummary so the transcript renders the assistant-bubble avatar from the pinned record snapshot; bumped runtime.rs size override 2001 → 2002 for the +1 line.

Reproduction Steps

1. Build the desktop app off this branch.
2. Open a channel with managed agent-session activity.
3. Observe the polished transcript: grouped items, tool-call summaries, assistant avatars, and density-aware markdown rendering.
4. Confirm ownership gating still behaves per fix(observability): gate agent observability on declared ownership, not key custody #1229 (managed agent OR declared NIP-OA owner sees the transcript).

Validation

• pnpm check (biome + file-sizes + px-text) ✓
• pnpm typecheck ✓
• pnpm test — 1183 pass / 0 fail ✓
• cargo check ✓
• All lefthook pre-commit + pre-push hooks ✓