Send #rss get summaries as 3-5 separate mesh messages (v0.21.0)

The single-message summary was too small (owner request). The summarizer
prompt now asks for exactly 3-5 lines, one item per line, in the format
'<short header>: <one or two short sentences>' with a <=20-char header,
no intro/outro/numbering. maxTokens stays 2500 (reasoning-token headroom).

The reply is parsed into items: drop empty lines and lines without a ':'
header separator, cap at 5; fewer than 3 valid lines sends what we got
(no failure/retry), zero valid lines sends nothing. Each item goes out as
its own mesh message via respond(id, line) - all threaded to the trigger
packet id on its channel. Per-item backstop fitOneLine() hard-cuts any
line >185 chars at a word boundary near 180 so every item fits one packet;
the old whole-reply fitOnePacket() cut is gone.

CommandService sends array replies line by line through the same routing
as single replies (respond per line, or legacy sendText fallback per line
when there is no packet id). LLM failure path unchanged: single
'summary failed' reply.

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## v0.21.0 — 2026-09-25 19:59
+
+- `#rss get <name|#tag>` now replies with **3–5 SEPARATE mesh messages** instead of one small summary (owner request: the single-message summary was too small). Each item is its own packet, so no fragmentation — and each rides the trigger's channel threaded as a quote of the command packet.
+- New summarizer prompt asks for exactly 3-5 lines, one item per line, format `<short header>: <one or two short sentences>` with a ≤20-char header (e.g. `Culture: Museum opens new wing`), no intro/outro/numbering. maxTokens stays 2500 (reasoning-token headroom — see v0.20.1).
+- The LLM reply is parsed into items: split on newlines, trim, drop empty lines and lines without a `:` header separator, cap at 5. Fewer than 3 valid lines → send what we got (no failure, no retry — the model is non-deterministic); zero valid lines → no message sent.
+- Per-item backstop replaces the old whole-reply cut: any single line >185 chars is hard-cut at a word boundary near 180 (`fitOneLine`), so every item fits one packet even if the model ignores the prompt. `fitOnePacket()` (whole-reply ≤190) is gone — it no longer applies to joined text.
+- CommandService now sends array replies line by line: each element goes through the same routing as a single reply (`respond(id, line)` threaded to the trigger packet id; legacy sendText fallback per line when there is no packet id). A failing send stops the remaining lines (warn log), like any failed command.
+- LLM failure path unchanged: single `summary failed` reply via respond(). `#rss get #tag` gets the same multi-message treatment automatically (shared summary path — covered by tests). All other subcommands unchanged.
+- Tests: 158 → 165 — prompt shape + maxTokens asserted on the new call, 5-item cap, invalid-line filtering, fewer-than-3 fallback, per-line over-length cut through `handle()`, direct `parseSummaryItems`/`fitOneLine` specs, and CommandService array-reply routing (threaded respond ×N to one packet id; legacy sendText fallback).
+
 ## v0.20.1 — 2026-09-25 19:20
 
 - `#rss get` summaries now fit ONE mesh packet (≤190 chars). Mesh fragments longer replies into fire-and-forget packets that recipients frequently never receive, and the old prompt ("a few short one-line highlights") produced ~326-334 char replies.