* fix(chat): skip empty assistant tool-call placeholder rows in REST transcript
Non-reasoning models (e.g. gemini-3.5-flash) store a tool-call turn as an
empty assistant row (content = "", no reasoning) with a tool_calls list.
The REST transcript returns these verbatim, and mapServerMessages was only
filtering empty assistant rows that carried reasoning text (the issue #771
thinking-model case). With no reasoning, the filter check failed and the
placeholder rows fell through — rendering as empty bubbles with Copy buttons
in the chat list.
Fix: skip ANY empty assistant row regardless of whether reasoning is present.
If it carries reasoning, stash it for folding (issue #771 path unchanged).
If it doesn't, it's a pure tool-call placeholder — silently drop it.
No user-visible content is lost: these rows never held displayable text.
Verified on device (hermes37 emulator): session 'Friendly greeting #9' had
10 ghost empty bubbles; after fix the transcript shows only real messages.
Issue: #956
* fix(chat): blank-content guard in FullBleedAgentMessage prose renderer
Defense-in-depth for the ghost-bubble fix (#953): never render an empty
prose block (blank text + lone Copy button) if a placeholder row ever
slips past upstream mapping. Streaming messages keep rendering so the
live cursor survives until the first delta lands.
Verified on device: cold start of 'Friendly greeting #9' renders only
real content — no empty bubbles.
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Co-authored-by: M57 <hy4ri@users.noreply.github.com>
