Add portable Line-us pen-arm support to ink-signature pipeline

Adds a second machine class (small fan-shaped reach arm) alongside the
CR-10/AxiDraw rectangular-bed plotters, so wet signatures can be produced
while away from the home station.

ink_signature_plotter.py:
- PlotterConfig gains dialect (marlin|lineus) + name; new LineUsConfig
  (native units, pen height = per-move Z, reach annulus from shoulder pivot).
- Named machine profiles (cr10 default, axidraw, lineus) via load_profile().
- bed_mm_to_lineus_units(), check_reach() (annulus for lineus, rectangle for
  marlin), compute_jig_offset_for_box() (solves jig from the ACTUAL fitted ink
  extent so a wide cell line doesn't over-constrain a small arm).
- emit_gcode() dispatches to emit_marlin_gcode()/emit_lineus_gcode().
- send_lineus(): WiFi TCP 1337 (NUL-terminated, ok-acked) or USB serial,
  dry_run=True default (same gating as the CR-10 path).

ink_signature_cli.py: --profile, --solve-jig (auto-applies jig offset),
--lineus-host/--lineus-usb, reach-check that refuses to --plot out-of-reach
on Line-us.

Tests: 43 checks (was 30) covering profiles, reach check, jig solve, lineus
emitter, dry-run sender. Docs updated with profiles + portable workflow.

scripts/tests/test_ink_signature.py

@@ -119,6 +119,53 @@ def main():
     g_big = ink.emit_gcode(ink.plan_signature(vector, big_box, cfg), cfg)
     check("over-bed plot warns", "outside the configured bed" in g_big)
 
+    print("profiles: cr10 / axidraw / lineus")
+    cr10 = ink.load_profile("cr10")
+    axi = ink.load_profile("axidraw")
+    lu = ink.load_profile("lineus")
+    check("cr10 is marlin Z-pen", cr10.dialect == "marlin" and not cr10.servo_pen)
+    check("axidraw is marlin servo + A4 bed", axi.dialect == "marlin" and axi.servo_pen and axi.bed_max_y_mm == 297.0)
+    check("lineus dialect + has LineUsConfig", lu.dialect == "lineus" and lu.lineus is not None)
+    raised = False
+    try:
+        ink.load_profile("nope")
+    except ValueError:
+        raised = True
+    check("unknown profile raises", raised)
+
+    print("Line-us reach check + jig solve")
+    # With the default jig (0,0), the CMS box (PDF ~48,443 pt) maps far outside
+    # the small arm's reach -> reach check should fail.
+    lu_planned_raw = ink.plan_signature(vector, BOX, lu)
+    rep_raw = ink.check_reach(lu_planned_raw, lu)
+    check("raw lineus plot is out of reach", rep_raw["dialect"] == "lineus" and not rep_raw["ok"])
+    # Solve the jig: should bring the whole cell into reach.
+    solved = ink.compute_jig_offset_for_box(BOX, lu, vector=vector)
+    check("solve-jig reports ok", solved["ok"] is True)
+    check("solve-jig returns jig offsets", "jig_x_mm" in solved and "jig_y_mm" in solved)
+    from dataclasses import replace as _replace
+    lu_fixed = _replace(lu, jig_x_mm=solved["jig_x_mm"], jig_y_mm=solved["jig_y_mm"])
+    lu_planned = ink.plan_signature(vector, BOX, lu_fixed)
+    rep_fixed = ink.check_reach(lu_planned, lu_fixed)
+    check("after solve-jig the signature is in reach", rep_fixed["ok"] is True)
+
+    print("Line-us G-code emission")
+    glu = ink.emit_gcode(lu_planned, lu_fixed)
+    check("lineus homes the arm", "G28" in glu)
+    check("lineus encodes pen height as Z in G01", "G01 X" in glu and f"Z{lu.lineus.pen_up_z:d}" in glu)
+    check("lineus uses pen-down Z", f"Z{lu.lineus.pen_down_z:d}" in glu)
+    check("lineus has no Marlin mm header", "G21" not in glu)
+    check("in-reach lineus plot has no reach warning", "fall outside the arm reach" not in glu)
+    # Out-of-reach plot should carry the warning comment.
+    glu_bad = ink.emit_gcode(lu_planned_raw, lu)
+    check("out-of-reach lineus plot warns", "fall outside the arm reach" in glu_bad)
+
+    print("Line-us sender is dry-run safe")
+    res_tcp = ink.send_lineus(glu, dry_run=True)
+    check("lineus dry-run does not send (tcp)", res_tcp["sent"] is False and res_tcp["transport"] == "tcp")
+    res_usb = ink.send_lineus(glu, serial_port="/dev/ttyACM0", dry_run=True)
+    check("lineus dry-run does not send (usb)", res_usb["sent"] is False and res_usb["transport"] == "serial")
+
     print("preview SVG")
     svg = ink.render_preview_svg(planned, cfg)
     check("svg has path(s)", "<path" in svg)