feat: track lifetime connect counters per scanner

[bluetoothbot]

What

Add lifetime connect counters to BaseHaScanner and surface them in
async_diagnostics():

• _connect_completed_total — successful connection attempts since this
  scanner was registered with the manager
• _connect_failed_total — failed connection attempts since registration
• _last_connect_completed_time — monotonic timestamp of the most recent
  successful connection (0.0 if none)

Why

CLAUDE.md flags this as a documented gotcha:

_connect_in_progress is the only per-scanner "busy" signal. There is
no counter of active or completed connections — only "does this scanner
have a connect attempt in flight right now".

That gap matters for the stuck-proxy class of bugs tracked in #340. The
existing per-address _connect_failures dict is cleared the moment a
later attempt succeeds, so a single diagnostics snapshot cannot tell you
whether this scanner has ever completed a connection in its current
registration. With these counters a snapshot can distinguish:

• busy proxy — slots=0/N free, connect_completed_total growing,
  last_connect_completed_time recent
• stuck proxy — slots=0/N free, connect_completed_total flat at
  zero, last_connect_completed_time ancient or 0.0

This complements the diagnostic work in #407 / #416 / #422 without
changing user-facing connection behavior.

How

• New attributes added to BaseHaScanner.__slots__ and mirrored in
  base_scanner.pxd to keep cython in sync.
• Counters bump in _finished_connecting (existing call site that
  already branches on connected); monotonic_time_coarse() records
  the success timestamp.
• _clear_connection_history() resets the new state alongside
  _connect_failures / _connect_in_progress, so the counters describe
  the current scanner-registration lifetime rather than the host
  process lifetime.
• async_diagnostics() exposes the three new fields next to the
  existing connect_in_progress / connect_failures keys.

Testing

• SKIP_CYTHON=1 poetry run pytest tests/ -W "error::DeprecationWarning" -W "ignore::DeprecationWarning:asyncio" → 250 passed, 1 skipped.
• New test test_lifetime_connect_counters_reset_on_history_clear
  exercises both the increment paths and the reset path.
• Existing test_diagnostics_surface_connect_state extended to also
  assert the new diagnostics keys.
• Diagnostic-shape assertions in test_manager.py and test_scanner.py
  updated for the three new keys.

🤖 Generated with Claude Code

---

Quality Report

Changes: 5 files changed, 67 insertions(+)

Code scan: clean

Tests: failed (FAILED)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.94%. Comparing base (47d4b71) to head (ea80a6d).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #433      +/-   ##
==========================================
+ Coverage   95.92%   95.94%   +0.01%     
==========================================
  Files          14       14              
  Lines        1913     1922       +9     
  Branches      232      232              
==========================================
+ Hits         1835     1844       +9     
  Misses         42       42              
  Partials       36       36              

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[codspeed-hq]

Merging this PR will improve performance by 5.94%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

#### 🎉 Hooray! `pytest-codspeed` just leveled up to 5.0.2!

A heads-up, this is a breaking change and it might affect your current performance baseline a bit. But here's the exciting part - it's packed with new, cool features and promises improved result stability 🥳!
Curious about what's new? Visit our releases page to delve into all the awesome details about this new version.

⚡ 1 improved benchmark
✅ 10 untouched benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_inject_100_simple_advertisements	206.9 µs	195.3 µs	+5.94%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing koan/scanner-lifetime-connect-counters (ea80a6d) with main (47d4b71)¹}

Footnotes

1. No successful run was found on main (fb03366) during the generation of this report, so 47d4b71 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩