fix(lsp): add poll retry for push-only diagnostics servers

[potb]

Closes #1522

Push-only LSP servers (e.g. Godot) return nothing on pull requests. When pull fails, we just return empty — but push diagnostics often arrive moments later.

Added a poll retry: on pull failure, check the diagnostics store every 200ms for up to 3s. Returns immediately when data arrives, falls back to empty on timeout (same as before).

[cubic-dev-ai]

1 issue found across 4 files

Confidence score: 4/5

• Safe to merge with low risk; the only issue is a low‑severity polling behavior and no other concerns were flagged.
• In src/tools/lsp/lsp-client.ts, the polling loop treats empty diagnostics as missing, which can force a full timeout even when the server reports a clean file, potentially slowing feedback.
• Pay close attention to src/tools/lsp/lsp-client.ts - polling loop ignores valid empty diagnostics and may wait unnecessarily.

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="src/tools/lsp/lsp-client.ts">

<violation number="1" location="src/tools/lsp/lsp-client.ts:114">
P2: Polling loop ignores valid empty diagnostics, forcing full timeout even when server reports a clean file.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[potb]

@cubic-dev-ai recheck

[cubic-dev-ai]

@cubic-dev-ai recheck

@potb I have started the AI code review. It will take a few minutes to complete.

[cubic-dev-ai]

2 issues found across 2 files

Confidence score: 4/5

• Behavioral impact is limited: the polling loop in src/tools/lsp/lsp-client.ts treats empty diagnostics as no update, so error-free files may wait an extra 3s before being considered updated.
• Test suite slowdown in src/tools/lsp/client.test.ts is minor and non-blocking, but it does add avoidable wait time each run.
• Pay close attention to src/tools/lsp/lsp-client.ts and src/tools/lsp/client.test.ts - polling logic and timer usage can introduce delays.

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="src/tools/lsp/lsp-client.ts">

<violation number="1" location="src/tools/lsp/lsp-client.ts:114">
P2: Polling loop ignores valid empty diagnostics updates, forcing a 3s timeout delay for error-free files.</violation>
</file>

<file name="src/tools/lsp/client.test.ts">

<violation number="1" location="src/tools/lsp/client.test.ts:302">
P3: This test will wait for the full diagnostics poll timeout (~3.5s) every run because timers aren’t mocked; it slows the test suite unnecessarily. Consider mocking setTimeout/using fake timers or overriding the timeout to keep the test fast.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}