Three small follow-ups to #3145, all observability/documentation —
zero behavior change:

1. src/gui/MainWindow.cpp — comment the asymmetric gating in the
   spotTriggered lambda. The TCI branch suppresses on lock / SWR
   sweep / missing slice because it must mirror AetherSDR's local-
   tune outcome (Log4OM cannot diverge from the radio's actual
   state). The radio branch delegates gating to the firmware via
   `spot trigger`. Without the inline note a future "DRY this up"
   pass could silently regress Log4OM behavior under lock or SWR
   sweep.

2. docs/architecture/tci-receivers.md — note that both
   `clicked_on_spot:` and `rx_clicked_on_spot:` are emitted
   unconditionally for every spot click. #3145 made dual emission
   the v2 protocol baseline (no client-capability negotiation),
   which matters for anyone writing a TCI protocol parser.

3. src/core/TciServer.cpp — qCWarning when notifySpotClicked()
   falls back to slices.first() because the caller passed a null
   slice. The MainWindow path always supplies one (guarded on `s`);
   only wireSpotModel's sliceForPanId(panId) can return nullptr.
   Today that silently mis-attributes rx_clicked_on_spot:'s `trx`
   field to slice 0 — invisible in single-slice testing, broken
   in multi-pan. The warning makes the edge case diagnosable in
   the field.

Principle I (FlexLib is the protocol authority) cited because the
dual `clicked_on_spot:` / `rx_clicked_on_spot:` emission and `trx`
indexing rules trace back to ExpertSDR3/TCI v2 spec authority that
#3145 codified — this commit documents that decision, it does not
revisit it.

Blast radius: risk_score=0.1845 on TciServer::notifySpotClicked
seed (4 high-risk callers: MainWindow::MainWindow,
MainWindow::wirePanadapter, SliceModel::sliceId, RadioModel::slices).
Verified the high-risk callers (MainWindow paths) only reach the
function via the non-null-slice arm and never trigger the new
warning branch; the only path that reaches the fallback is the
in-file wireSpotModel lambda when sliceForPanId returns nullptr.
No behavior change for any caller.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

…ethersdr#3145)

## Summary

This fixes the Log4OM TCI spot-click flow where Log4OM can inject a spot
into AetherSDR, AetherSDR tunes when the user clicks that spot on the
panadapter, but Log4OM never receives a spot-click notification back to
populate its logging fields.

AetherSDR already accepted TCI `spot:` messages and rendered them
locally, but those spots use synthetic local IDs. When the user clicked
one, the UI attempted to send `spot trigger <id>` to the Flex radio. The
radio does not know those local TCI spot IDs, so there was no
radio-origin `spot ... triggered` status echo, and therefore the TCI
server never emitted `clicked_on_spot` back to connected clients.

This also adds spot event compatibility with RUMlogNG, Swisslog for
Windows, LogHX and LogHX3, similar to Thetis implementation.

## What Changed

- Added `TciServer::notifySpotClicked(...)` so UI paths can explicitly
notify TCI clients when a locally rendered spot is clicked.
- Centralized TCI spot-click formatting in the TCI server and now emits
both forms used by Thetis / TCI clients:
  - `clicked_on_spot:<callsign>,<frequency_hz>;`
  - `rx_clicked_on_spot:<receiver>,0,<callsign>,<frequency_hz>;`
- Updated the existing `SpotModel::spotTriggered` wiring so radio-origin
spot trigger echoes also send the receiver-qualified
`rx_clicked_on_spot` form.
- Updated the panadapter spot-click path so TCI-origin spots skip the
invalid Flex `spot trigger 10000...` command and notify TCI clients
directly instead.
- Documented the receiver/channel behavior in the TCI receiver
architecture note.

## Protocol Behavior

The implementation mirrors the Thetis behavior and the TCI standard
shape:

- TCI clients send spots with
`spot:<callsign>,<mode>,<frequency_hz>,<color>,<text>;`.
- AetherSDR stores those as local `source=TCI` spots.
- When the user clicks the rendered spot, AetherSDR tunes the slice
through the existing spectrum-click path.
- AetherSDR then broadcasts the clicked spot notification to all
connected TCI clients.

The receiver value in `rx_clicked_on_spot` uses the same contiguous TCI
`trx` index policy as `vfo:` and `modulation:`. The channel is currently
`0`, matching AetherSDR's single-VFO path for the slice.

## Validation

- `git diff --check`
- Configured a fresh macOS build with the pinned Command Line Tools SDK:
- `cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo
-DCMAKE_OSX_SYSROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk`
- Built the app successfully:
  - `cmake --build build --target AetherSDR -j22`

👨🏼‍💻 Generated with OpenAI Codex (GPT-5.5 Pro 4/23) and tested by
@jensenpat

Co-authored-by: Codex <noreply@openai.com>