Make Channel the single source of truth for a reading's name

Device tab stays hardware-only (pins, wiring, may vary per workstation);
the Channels window owns the profile-facing identity. Concretely:

- Fix a real regression: SerialDevice generic-format Apply & Reconnect
  nulled out custom channel_names/units every time (no fallback, unlike
  every other optional field in reconfigure()), silently reverting to
  sig0/sig1/... ids.
- Plot legend now live-tracks the current Signal/Channel name instead of
  freezing tr.label at add-time, so a rename shows up without re-adding
  the trace.
- Add an inline quick-reconnect (combo + button, pre-selects the actual
  current source) directly on each Channel block in the Channels window,
  for the common single-source case — rewiring hardware no longer means
  touching every Plot/pipeline that referenced it.
- Collapse the Channel ID field behind an "ID ▸" advanced toggle;
  channel_id is already auto-derived from the name (_slug_id) and rarely
  needs to be seen.
- Devices tab's Signal "Name" column relabeled "Label" with a tooltip —
  de-emphasized now that Channel name is the real identity.
- Move "create a Channel from this Signal" from a column on the Devices
  tab's signal table to a ⊕ button on each Signal row in the Channels
  tab's Namespace panel — the action now lives where the identity is
  created, not on the hardware tab. Only that instance opts in
  (on_create_channel); the read-only Namespace dock on the main window
  is unaffected.
- Floor the Namespace panel's width at its columns' natural size so
  dragging the Channels-tab splitter narrower can't push the ⊕ column
  behind the horizontal scrollbar.
- Breadcrumb log when a profile-saved Signal override can't be applied
  because the signal_id no longer exists.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/core/profile.py b/core/profile.py
index c77e646..da0f478 100644
--- a/core/profile.py
+++ b/core/profile.py
@@ -393,6 +393,8 @@ class ProfileManager:
                 continue
             ch = dev.get_signal(ch_data["signal_id"])
             if not ch:
+                print(f"[Profile] '{ch_data['device_id']}': signal '{ch_data['signal_id']}' "
+                      f"no longer exists — saved override for '{ch_data.get('name', '?')}' dropped")
                 continue
             ch.name    = ch_data.get("name", ch.name)
             ch.unit    = ch_data.get("unit", ch.unit)