fix(parser): surface task-notification wrapped in system-reminder (v2.1.234+)

[delexw]

What

Claude Code v2.1.234 changed how between-turn background-task notifications are delivered: they now arrive fully wrapped in <system-reminder>...</system-reminder> tags, matching the wrapping mid-turn delivery already used, instead of the previous unwrapped <task-notification>...</task-notification> format.

is_user_noise() treats any user entry that both starts with <system-reminder> and ends with </system-reminder> as pure harness-reminder noise and drops it entirely. Once a task notification is wrapped this way, it matches that rule and gets silently dropped instead of surfacing as the informational System message it used to produce — losing the task's completed/failed/killed status from the trace view.

Fix

• Added unwrap_system_reminder() in classify.rs, which strips a full <system-reminder>...</system-reminder> wrapper when the entire trimmed content is exactly that wrapper.
• is_user_noise() now checks the unwrapped inner content for a <task-notification> prefix before treating a <system-reminder>-wrapped entry as noise, so it falls through instead of being dropped.
• The existing TASK_NOTIFICATION_TAG dispatch in classify() also checks the unwrapped content, so the wrapped notification still classifies as a System message with the correct is_error status (failed → error, completed/killed → informational).
• Plain reminders with no task-notification inside are unaffected and still dropped as before.

Tests

Added three regression tests in classify.rs:

• a <task-notification> wrapped in <system-reminder> still classifies as a System message
• a wrapped failed notification still sets is_error: true
• a plain wrapped reminder (no task-notification) is still dropped as noise

Verification

• npx tsc --noEmit, npx oxlint, npx oxfmt --check — clean
• cargo clippy --manifest-path src-tauri/Cargo.toml -- -D warnings — clean
• cargo fmt --manifest-path src-tauri/Cargo.toml --check — clean
• vitest run — 498 passed
• cargo test --manifest-path src-tauri/Cargo.toml — 690 passed (including the 3 new tests)
• claude --debug -p "say hello" ran cleanly with no crash/panic in the trace-capture path

Fixes #262