perf: skip redundant coordinator state resets + bump version to 0.4.9

[Qubitium]

Summary

This PR contains two changes:

1. Performance: Reduce per-row logging/column overhead by shrinking the count == 0 fast path in _clear_progress_stack_locked. When there is no rendered progress stack, the function only needs to restore cursor visibility and flush any deferred log records. It was also re-clearing six coordinator state fields on every log/column row even though those fields are reset when the stack is actually cleared by the render paths. Dropping those redundant __setattr__ calls removes a measurable chunk of per-row latency for the column and log APIs.

if count == 0:
    if show_cursor:
        _set_cursor_visibility_locked(True, backend_state=state)
    if flush_deferred_logs and not for_log_output:
        _flush_deferred_logs_locked()
    return

2. Version: Bump pyproject.toml version from 0.4.8 to 0.4.9.

Profiling

Local cProfile harness (1000 iterations per API, 120 columns):

API	Before this pass	After this pass
progress snapshot	0.076 s	0.077 s
progress iter	0.094 s	0.090 s
columns	0.138 s	0.126 s
logs	0.064 s	0.058 s

Progress paths are essentially unchanged; column and log paths gain ~9% and ~10% respectively.

All 141 tests pass locally.

Link to Devin session: https://app.devin.ai/sessions/45e5067b04374a8381566d710d0311da
Requested by: @Qubitium

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✅ Devin Review: No Issues Found

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