Video calls (PairUX→ASCII), agent@ chat, and finger routes

ssh video-<code>@ joins a PairUX/LiveKit call rendered as truecolor
ASCII (▀ half-blocks, 2 pixels per cell); video@ prompts for a code.
Codes are minted by PairUX only. Pipeline: VP8 RTP → PLI keyframe
requests → ivfwriter remux → ffmpeg decode/scale → RGB24 → ANSI →
bubbletea over the SSH PTY. Subscriber-only, no audio in v1.

ssh agent@ opens a persisted chat with the operator's agent —
AGENTBBS_AGENT_CMD runs per message (stdin→stdout), e.g. `claude -p`.

ssh <member>@ with someone else's name prints a classic finger card
(.plan, member since, last seen) and disconnects; your own name still
enters the hub.

cmd/lkpublish: dev publisher for testing (explicit -fps pacing; lksdk
IVF replay mispaces from file timebase alone, measured 1fps from a
15fps file; dimensions required or dynacast pauses the track).

Verified end-to-end against livekit-server --dev: 128k truecolor cells
/ 20k distinct colors streamed over a real SSH session; chat round-trip
and finger card verified over SSH. Go toolchain pinned to 1.26 via
mise.toml (lksdk requirement).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/ascii/ascii.go

@@ -0,0 +1,52 @@
+// Package ascii converts raw video frames into truecolor terminal art.
+//
+// Each character cell renders two vertical pixels using the upper-half block
+// (▀): foreground colors the top pixel, background the bottom — the same
+// technique doom-ascii uses. A WxH terminal therefore displays a Wx(2H)
+// pixel image.
+package ascii
+
+import (
+	"fmt"
+	"strings"
+)
+
+// FrameRGB renders a packed RGB24 frame (w*h*3 bytes, as ffmpeg's rawvideo
+// rgb24 emits) sized exactly for the target cell grid: w columns, h*2 rows
+// of pixels. Rows are joined with \r\n so the output is PTY-safe.
+func FrameRGB(buf []byte, w, h int) string {
+	if len(buf) < w*h*3 || w <= 0 || h <= 0 {
+		return ""
+	}
+	rows := h / 2
+	var b strings.Builder
+	b.Grow(rows * w * 40)
+	for row := 0; row < rows; row++ {
+		top := row * 2
+		bot := top + 1
+		for x := 0; x < w; x++ {
+			ti := (top*w + x) * 3
+			bi := (bot*w + x) * 3
+			fmt.Fprintf(&b, "\x1b[38;2;%d;%d;%dm\x1b[48;2;%d;%d;%dm▀",
+				buf[ti], buf[ti+1], buf[ti+2],
+				buf[bi], buf[bi+1], buf[bi+2])
+		}
+		b.WriteString("\x1b[0m")
+		if row != rows-1 {
+			b.WriteString("\r\n")
+		}
+	}
+	return b.String()
+}
+
+// FitEven clamps a terminal geometry to an even pixel height for the
+// half-block renderer and returns pixel dimensions (pw, ph) for the decoder.
+func FitEven(cols, rows int) (pw, ph int) {
+	if cols < 8 {
+		cols = 8
+	}
+	if rows < 4 {
+		rows = 4
+	}
+	return cols, (rows - 1) * 2 // leave one status line
+}