refactor(macos): dedupe the cancellable fail-soft pattern in present/_present_status

[dhruvbatra]

Issue

MacOSPresentationController.present and _present_status (yutori/navigator/macos/presentation.py) each wrapped their dispatch body in the identical

except asyncio.CancelledError:
    raise
except Exception as error:  # noqa: BLE001 - presentation is fail-soft
    await self._degrade(f"presentation_failed:{type(error).__name__}", error)

block. This is the same duplication class the _fail_soft decorator (#373) already consolidated for show_thumbnail/before_capture/after_capture/encode_observation — those four methods explicitly couldn't reuse _fail_soft because they need to reraise CancelledError before degrading, so the pattern was left duplicated in these two methods instead.

Improvement

Extracted a new _fail_soft_cancellable decorator — the cancellation-aware counterpart to _fail_soft — and applied it to both present and _present_status. Each method now keeps only its distinct dispatch body.

Why it's safe

• No behavior change. The removed try previously wrapped only the code below each method's early-return guards (e.g. if not self._status.available or self._stopping: return); those guards are simple attribute checks that cannot raise, so moving them inside the decorated body is equivalent. The exception handling order (reraise CancelledError, else degrade with the same f"presentation_failed:{type(error).__name__}" reason) is byte-for-byte preserved.
• Verified: full suite passes unmodified — 914 passed, 3 skipped, 1 deselected (same as baseline). ruff check and ruff format --check both clean on the touched file.
• Scope: 1 file changed, mechanical extraction only, no public API change (both are internal controller methods).

Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com

🤖 Generated with Claude Code

https://claude.ai/code/session_01NoGweAuMDdcoLXYHWgfY3j

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Generated by Claude Code

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Note

Low Risk
Mechanical refactor in internal macOS presentation error handling with preserved cancellation and degrade semantics; no API or logic changes described.

Overview
Introduces _fail_soft_cancellable, a decorator that re-raises asyncio.CancelledError and otherwise degrades with the same presentation_failed:{exception} reason used before, matching the cancellation-aware branch that was duplicated on present and _present_status.

Both methods drop their inline try/except blocks and are annotated with the new decorator so only event-dispatch logic remains. The _fail_soft docstring now points readers at _fail_soft_cancellable for methods that must not treat cancellation as a presentation failure.

No intended behavior change—exception order and degrade messaging are preserved; early-return guards now run inside the decorated wrapper (still safe for the existing guard checks).

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