Route a friend's plain face-room line like the owner's: routed, single pass, no follow-ups

[Birfy]

Fixes #462

What: A friend's attested plain line in a face-to-face room now goes through the same routing (#299) and single-pass no-follow-up rule (#295) as the owner's own line (owner decision 2026-10-20).

Why: postHuman posts the friend's line from the quiet face-notice sender, so it reached the round with botId: 'face-notice'. isPlainFaceLine returned false before its plain check, so the round got no route (up to 6 Bots answered, no last-speaker-first) and no single (a Bot's @ in its answer could call another Bot on). The relay could also pick a Bot post queued with the friend's line as the opener.

How (core/src/host/groups.js):

• friendLine(post): face-notice sender carrying human. isPlainFaceLine reads such a line by plain, so it gets route (fallback: false, so nothing is forced on this home), single, lastFirst and its faceLine (still guarded by the friend's authorId, Face room: held Bot replies show as sent bubbles before approval and a rejected one stays; one Bot answers a single line twice #456).
• The opener pick treats a friend's line that asks my Bots (plain or callIds) as a person's line, not an event, so it picks the speakers over a Bot post queued with it.
• A friend's @Bot line (callIds) and an unattested line are unchanged.

Test: new #462 test in core/test/rounds.test.js (routed prompt, one answer, the reply's @Chief starts no turn, last speaker first on a follow-up, the friend's line wins over a queued Bot post, @Writer from a friend is unrouted and starts only the Writer). It fails on main. The #295 test now expects one answer to the friend's plain line instead of two. ARCH_DOCS_BASE=origin/main TZ=UTC npm run verify: pass (core 1018, social 276, tree 80, timeline 80, scripts 88, interop 37, live-e2e 16; 0 failures). Patches regenerated and checked; docs (core-host, social) and a changelog fragment updated.

Risk tier: T2 (estimate; the controller sets the label)

[Birfy]

Self-review: PASS
Tip SHA: 65bdf1c
Ran:

• ARCH_DOCS_BASE=origin/main TZ=UTC npm run verify (Node 24): pass, 0 failures (core lint + arch-docs OK, plugin lint, build-client --check, ds-bot-patches check, core 1018, social 276, tree 80, timeline 80, .github scripts 88, interop 37, live-e2e 16)
• New #462 test in core/test/rounds.test.js fails on main (no route on the friend's line) and passes here
• node scripts/ds-bot-patches.mjs generate + check; node .github/scripts/changelog.mjs check
• CI at the tip: all checks green (tests-ok pass); risk-gate reports T2
• Diff re-read against the owner design rules: only face-room routing of a friend's attested line changes; no UI, approval, grant or connector change; Bot-sent lines still go through the usual hold / Auto-send rules
  Not run:
• Live two-home check on the Mac instances (3080/3081) or against production Bot Social
• Smoke bench (dev/bench.sh smoke)