fix: handle Claude Agent SDK 0.3.x system messages to stop runtime-warning flood

[imabdulazeez]

What Changed

Teach the Claude adapter about the system message subtypes added in the
@anthropic-ai/claude-agent-sdk 0.3.x bump, so they stop falling through to the
generic "Unhandled subtype" runtime warning:

• thinking_tokens → no-op. This is the one the SDK streams continuously while a
  model is in its extended-thinking phase, and is responsible for the nonstop
  warnings on every prompt.
• permission_denied → emits a new dedicated tool.denied provider-runtime event.
• mirror_error → mapped to runtime.error.

Adds the tool.denied runtime event (contract + ingestion) so a denied tool shows
up as a distinct, error-toned work-log entry (tool name + reason) instead of a
generic "Runtime warning".

Why

The 0.3.x SDK introduced new system message subtypes. ClaudeAdapter's
handleSystemMessage switch only knows the older set, so anything new hits the
default branch and emits a runtime.warning. thinking_tokens is emitted
repeatedly throughout a model's thinking, so every prompt floods the work log with
"Runtime warning" entries — exactly what's reported in #2870.

Handling the three new subtypes explicitly removes the noise while keeping the
default branch as a catch-all so genuinely-unknown future messages are still
surfaced. permission_denied and mirror_error are real signals, so they're routed
to meaningful events rather than silently dropped.

Fixes #2870

UI Changes

No visual/component changes. Behavioral only: the work log no longer fills with
repeated "Runtime warning" entries on every prompt (the "before" is the screenshot
in #2870), and a denied tool now renders as a distinct error-tone entry.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (N/A — no visual changes; "before" is the screenshot in [Bug]: I keep getting runtime warnings since yesterday #2870)
• I included a video for animation/interaction changes (N/A)

Note

Handle Claude Agent SDK 0.3.x system messages to stop runtime-warning flood

• Adds thinking_tokens, permission_denied, and mirror_error subtypes to the system message handler in ClaudeAdapter.ts: thinking_tokens is silently ignored, permission_denied emits a new tool.denied runtime event, and mirror_error emits a runtime error instead of an unhandled warning.
• Introduces the tool.denied event type in providerRuntime.ts with a payload carrying toolName, toolUseId, reason, and agentId.
• Maps tool.denied events to an error activity in ProviderRuntimeIngestion.ts, surfacing the tool name and denial reason in the activity summary.

^{Macroscope summarized 423af15.}

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