refactor(settings): route SettingsDefaults diagnostics through emitDiagnostic

[darion-yaphet]

Summary

SettingsDefaultsManager is a base-layer library module (runs under the worker daemon and hooks) that emitted its [SETTINGS] diagnostics via raw console.warn. Those lines can be swallowed by the Phase 2 hook stderr buffer (#2292).

Replace the 5 console.warn calls with emitDiagnostic (from hook-io):

• Survives the Phase 2 hook stderr buffer (Hooks silently block every Claude Code event with No stderr output once recordWorkerUnreachable threshold trips #2292) — the same channel logger itself uses, instead of being swallowed by raw console.
• Preserves the deliberate stderr-not-stdout behavior that protects the machine-readable JSON contract on stdout (CLI commands like start promise JSON on stdout to the hook framework).

Why emitDiagnostic, not logger

logger transitively depends on this module (logger → shared/paths → SettingsDefaultsManager). Importing logger here would invert the layering and risk a circular dependency at bootstrap. hook-io is a leaf module (type-only import), so there is no cycle.

Scope note

This was scoped deliberately. Of 546 console.* calls in src/, the vast majority are correct and intentionally left as-is:

• worker-service.ts / ServerBetaService.ts — CLI entrypoints; console.log(JSON.stringify(...)) is the program's stdout output contract. Routing to the file logger would silence the CLI.
• npx-cli/**, *Installer.ts, bin/** — user-facing CLI / install-time output.
• ui/viewer/** — browser React code; the Node file-based logger cannot run there.
• utils/logger.ts, shared/hook-io.ts — the logger's own stderr fallback.

Verification

• tsc --noEmit clean
• npm run build green
• bun test — 39 pass / 0 fail (incl. settings-defaults-manager.test.ts and logger-usage-standards.test.ts)
• [SETTINGS] diagnostics confirmed still printing to stderr in test output

[greptile-apps]

Greptile Summary

This PR replaces five console.warn calls in SettingsDefaultsManager with emitDiagnostic from hook-io.ts, ensuring [SETTINGS] diagnostic lines bypass the Phase 2 hook stderr buffer (#2292) instead of being silently dropped.

• Buffer bypass: emitDiagnostic routes through pinnedBypassWrite (the real fd writer captured before the buffer was installed), so diagnostics now survive the hook stderr capture window. In non-hook contexts (worker daemon, CLI), pinnedBypassWrite is null and the function falls back transparently to process.stderr.write, preserving existing behavior.
• Layering preserved: hook-io.ts has only an import type of cli/types.ts, so there is no runtime dependency that could form a cycle with logger → shared/paths → SettingsDefaultsManager.

Confidence Score: 5/5

Safe to merge; the change is a targeted swap of one output channel for another with no logic changes.

All five substitutions are mechanically correct: newlines are explicitly appended (bypassing the implicit newline that console.warn provides), message content is preserved exactly, and emitDiagnostic correctly falls back to process.stderr.write in non-hook contexts where pinnedBypassWrite is null. The hook-io import carries no runtime dependencies that could form a cycle. Existing tests cover stdout discipline and all settings-loading paths; they continue to pass.

No files require special attention.

Important Files Changed

Filename	Overview
src/shared/SettingsDefaultsManager.ts	Replaces 5 console.warn calls with emitDiagnostic; newlines are explicitly appended, message content is preserved, and the import of hook-io introduces no circular dependency.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant Hook as Hook Invocation
    participant SDM as SettingsDefaultsManager
    participant HookIO as hook-io (emitDiagnostic)
    participant Buffer as Stderr Buffer
    participant RealStderr as Real stderr (fd)

    Hook->>Buffer: installHookStderrBuffer()
    Hook->>SDM: loadFromFile(path)
    SDM->>HookIO: emitDiagnostic("[SETTINGS] ...")
    Note over HookIO: pinnedBypassWrite != null
    HookIO->>RealStderr: bypassWrite(line)
    RealStderr-->>Hook: Diagnostic visible

    Note over Hook,RealStderr: Before this PR (console.warn path)
    SDM--xBuffer: console.warn captured by buffer
    Buffer--xRealStderr: drop() on success — diagnostic lost

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sequenceDiagram
    participant Hook as Hook Invocation
    participant SDM as SettingsDefaultsManager
    participant HookIO as hook-io (emitDiagnostic)
    participant Buffer as Stderr Buffer
    participant RealStderr as Real stderr (fd)

    Hook->>Buffer: installHookStderrBuffer()
    Hook->>SDM: loadFromFile(path)
    SDM->>HookIO: emitDiagnostic("[SETTINGS] ...")
    Note over HookIO: pinnedBypassWrite != null
    HookIO->>RealStderr: bypassWrite(line)
    RealStderr-->>Hook: Diagnostic visible

    Note over Hook,RealStderr: Before this PR (console.warn path)
    SDM--xBuffer: console.warn captured by buffer
    Buffer--xRealStderr: drop() on success — diagnostic lost

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_{Reviews (1): Last reviewed commit: "refactor(settings): route diagnostics th..." | Re-trigger Greptile}

[thedotmack]

Merged into the community-edge branch — claude-mem's bleeding-edge release line. Closing here since your change now lives on that branch. See the branch model (community-edge → core-dev → main): https://docs.claude-mem.ai/branches . Thanks for the contribution! 🙏