feat: the U cell plays pushed UDP RTP on port 5600, first in decoding priority (#87, #94)

[compot-dev]

Closes #87, closes #94.

• U cell = real cell. The ninth cell of the 3×3 grid is now a multi-view cell like the slots (index U_CELL = 8, CELL_COUNT = 9) that listens on udp://@:5600 through the receiver of feat: receive plain RTP from Majestic outgoing over UDP, unicast and multicast (#68) #72. It decodes, gets corner text, takes part in the Multi-view: adaptive decoding — full rate or key frames per cell, learnt device capacity #85 planner (lowest priority until Decoding priority: the U stream first once data arrives #94) and in the debug page / /stats.json (slot: "U") and snapshots.
• U view (menu U): a grid of one cell — the U cell full-screen, same receiver. Leaving it (a slot, Q, pause) stops it.
• Hint until the first frame: "Send the camera's RTP/UDP output to" with every IPv4 address of the device (all interfaces that are up, no loopback / link-local, NetInfo.addresses() from feat: debug HTTP server on port 8085, LAN clients only (#96) #97), one per line; this device:5600 if there is none. Refreshed once a second while shown, so a new DHCP lease or a cable/Wi‑Fi switch appears without restarting the grid.
• No long-press audio on the U cell (video only).
• Removed: localIpv4() (first site-local address only) and the static hint view.
• READMEs (EN/RU/ZH) and unit tests (udpHintText with zero / one / two addresses; U cell constants).

Note: a slot with udp://@:5600 and the U cell would both bind port 5600; use another port in slots.

Device check: Majestic outgoing from a lab camera to udp://<box>:5600 → picture in the ninth cell and in the U view; hint with the box's address before the stream; debug page.

• Priority (Decoding priority: the U stream first once data arrives #94, Qodo on this PR): once the U cell's stream plays, it comes first in the Multi-view: adaptive decoding — full rate or key frames per cell, learnt device capacity #85 planner (before the audio cell and the slots); while it receives nothing it stays last and takes no share.

Device check (Aceline-1, build 7607ce8): Majestic outgoing on .165 to udp://172.17.32.144:5600 → the ninth cell plays it (H.265 1920×1088), /stats.json lists it as slot U, transport UDP; Majestic reports the destination live.

[compot-dev]

/review

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Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (1) 🎨 UX issues (0) 🔗 Cross-repo conflicts (0) 📜 Skill insights (0)

1. Active U streams lose planner priority 📎 Requirement gap ➹ Performance

Description

createQuadCells() always adds the U stream at index 8, while planDecoding() orders cells by
index after the optional audio cell. When U receives frames, it follows every configured slot and
any selected audio cell, so lower-priority streams can be promoted first.

Code

android/app/src/main/java/com/openipc/decoder/Decoder.java[R797-803]

+        quadCells = new QuadCell[CELL_COUNT];
+        for (int i = 0; i < CELL_COUNT; i++) {
         if (quadViews[i] == null) continue;
-            String url = mHosts[i];
+            String url = i == U_CELL ? UDP_CELL_URL : mHosts[i];
         if (url == null || url.isEmpty() || url.equals(DEFAULT_URL)) continue;
-            quadCells[i] = new QuadCell(i, url, mTransports[i], quadViews[i], framePool, mUserAgent,
+            Transport.Mode mode = i == U_CELL ? Transport.Mode.UDP : mTransports[i];
+            quadCells[i] = new QuadCell(i, url, mode, quadViews[i], framePool, mUserAgent,

Evidence

The changed cell creation code starts the U receiver at index 8, while the planner's branch
implementation adds the audio cell first and then iterates from index 0 upward, leaving U after all
slots.

Prioritize active U stream decoding
android/app/src/main/java/com/openipc/decoder/Decoder.java[797-803]
android/app/src/main/java/com/openipc/decoder/Decoder.java[984-1000]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
The U stream is appended at index 8 and the decode planner still schedules cells by audio selection followed by index order, so an active U stream is not prioritized ahead of slots as required by PR Compliance ID 1.
## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/Decoder.java[797-803]
- android/app/src/main/java/com/openipc/decoder/Decoder.java[984-1000]
## Recommended Fix
Build the planner order with an active, connected U cell first, then the audio-selected cell, then ordinary slots. Ensure the U cell is only treated as active when it is receiving and decoding data, while preserving the existing promotion and demotion behavior for all other cells.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

2. The hint test suite no longer compiles ✓ Resolved

Description

Decoder.udpHintText(List, int) replaces the string-based signature, but
udpCellHintNamesPortAndAddress() still passes a string for its address case and null for its
fallback case. The string argument prevents the test sources from compiling, so the new zero-, one-,
and multiple-address tests cannot run.

Code

android/app/src/main/java/com/openipc/decoder/Decoder.java[R787-792]

+    static String udpHintText(List<String> ips, int port) {
+        StringBuilder target = new StringBuilder();
+        for (String ip : ips) target.append('\n').append(ip).append(':').append(port);
+        if (target.length() == 0) target.append("\nthis device:").append(port);
+        return "UDP RTP \u00b7 port " + port + "\nWaiting for a stream\u2026\n\n"
+                + "Send the camera's RTP/UDP output to" + target;

Evidence

The production formatter now accepts List and has no string overload, while the existing test
still passes "192.168.1.20" at line 54, which Java cannot convert to a list. The newly added tests
use lists but leave that earlier call unchanged; the existing fallback case also still passes
null.

Refresh U hint addresses on network changes and test formatting
android/app/src/main/java/com/openipc/decoder/Decoder.java[786-792]
android/app/src/test/java/com/openipc/decoder/QuadGridTest.java[50-56]
android/app/src/test/java/com/openipc/decoder/QuadGridTest.java[52-74]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
The hint formatter now accepts a list of addresses, but an existing test still passes a string for its address case, preventing the test sources from compiling.
## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/Decoder.java[786-792]
- android/app/src/test/java/com/openipc/decoder/QuadGridTest.java[50-59]
## Recommended Fix
Update the existing test to pass `Collections.singletonList("192.168.1.20")` for the one-address case and `Collections.emptyList()` for the fallback case, or provide a compatible overload if preserving the old API is intentional. Keep the added zero-, one-, and multiple-address assertions, then run the unit tests.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

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[qodo-free-for-open-source-projects]

1. Active u streams lose planner priority 📎 Requirement gap ➹ Performance

createQuadCells() always adds the U stream at index 8, while planDecoding() orders cells by
index after the optional audio cell. When U receives frames, it follows every configured slot and
any selected audio cell, so lower-priority streams can be promoted first.

Agent Prompt

## Issue description
The U stream is appended at index 8 and the decode planner still schedules cells by audio selection followed by index order, so an active U stream is not prioritized ahead of slots as required by PR Compliance ID 1.

## Fix Focus Areas
- android/app/src/main/java/com/openipc/decoder/Decoder.java[797-803]
- android/app/src/main/java/com/openipc/decoder/Decoder.java[984-1000]

## Recommended Fix
Build the planner order with an active, connected U cell first, then the audio-selected cell, then ordinary slots. Ensure the U cell is only treated as active when it is receiving and decoding data, while preserving the existing promotion and demotion behavior for all other cells.

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

[compot-dev]

Qodo finding 1 (Active U streams lose planner priority) is fixed in effd3d0: the U cell comes first in the planner once its stream plays (#94). Device check (Aceline-1, effd3d0): U at full rate (.165 pushed H.265 1080p30), slots 1–8 on key frames within the learnt capacity.