Rework the WebSocket page and document /json/live deprecation

[bharvey88]

Fixes #241.

/json/live is not a normal alternative to the websocket stream: since 0.15 it only exists in custom builds with -D WLED_ENABLE_JSONLIVE (auto-enabled by -D WLED_DISABLE_WEBSOCKETS). The page now says so and points readers at the {"lv":true} stream.

While in there, reworked the rest of the page against the v16.0.1 source (ws.cpp):

• Documented the Peek stream's binary frame format, frame interval, and downsampling limits (1024 LEDs on ESP32, 256 on ESP8266)
• Documented binary realtime input over the socket (DDP tested, E1.31/Art-Net marked untested in source)
• Corrected the client limit (8 on ESP32, 3 on ESP8266, was "4") and mentioned info.ws
• Added the inbound frame size limit, error responses, the p/pong heartbeat, the ~1s broadcast coalescing, and a note that there is no wss://
• Added a minimal browser JS example

Detail that would clutter the flow sits in Akemi annotations, following the pattern from #347.

Summary by CodeRabbit

• Documentation
  • Expanded the WebSocket guide into a comprehensive protocol reference.
  • Added details on endpoint behavior, state broadcasts, rate limits, command responses, and frame-size errors.
  • Documented heartbeats, browser usage, binary LED previews, downsampling, realtime input, and platform-specific connection limits.
  • Clarified /json/live deprecation and fallback behavior.
  • Added guidance for trailing frame bytes and handling command acknowledgements without state data.

[coderabbitai]

Walkthrough

The WebSocket documentation now covers connections, state updates, commands, heartbeats, browser clients, binary LED streaming, realtime input, /json/live deprecation, and platform-specific limits.

Changes

WebSocket protocol reference

Layer / File(s)	Summary
Connection and message handling docs/interfaces/websocket.md	Documents /ws connections, state updates, JSON commands, frame limits, buffer errors, heartbeat handling, and oversized messages.
Browser and binary protocols docs/interfaces/websocket.md	Adds browser JavaScript usage and documents LED preview frames, downsampling, and realtime input packets for DDP, E1.31/sACN, and Art-Net.
Legacy endpoint and connection limits docs/interfaces/websocket.md	Describes /json/live deprecation and fallback behavior, plus platform-specific client limits and info.ws semantics.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: 🟡 Moderate · up to 1d2d9

The page documents a WebSocket API and example usage, but the current example can fail on valid responses and the stated matrix dimensions can cause clients to truncate or misrender data for odd-sized sources. These bounded correctness issues should be fixed or explicitly accepted before merging.

Poem

A rabbit checks each socket bright,
As state frames hop through day and night.
Commands reply,
LED colors fly,
And docs keep every path in sight.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the WebSocket documentation rework and the /json/live deprecation, which are the main changes.
Linked Issues check	✅ Passed	The documentation explains the /json/live limitation with WebSockets and directs users to the supported WebSocket live stream, addressing issue #241.
Out of Scope Changes check	✅ Passed	The additional WebSocket details support the documentation rework and remain related to issue #241 and the stated pull request objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 1

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Inline comments:
In `@docs/interfaces/websocket.md`:
- Around line 73-78: Update the `/json/live` deprecation note and its footnote
to explicitly state that WebSockets must be disabled for the endpoint to work,
while preserving the existing custom-build and fallback configuration details.

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• docs/interfaces/websocket.md

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[softhack007]

side note: the statement is correct, currently 1024 is a hard-coded limit for live preview.

In WLED-MM we found that an esp32 can handle 4096 live LEDs, and 8192 are possible on PSRAM boards when reducing the update rate to 120ms. We might add a "HD preview" option in the future, maybe together with backporting the in-line preview from WLED-MM.