Add retrying value assertions (expect.poll with matchers)

[JE-Chen]

assert_eventually only polls the framework's fixed dict-spec checks (text/image/pixel/window/clipboard/process/file/http). It can't retry an arbitrary value — an OCR'd total equalling a string, a row count stabilising, a custom predicate.

• expect_poll(getter, matcher, ...) → PollResult (ok/value/attempts/waited_s); assert_poll raises on timeout. Injectable clock/sleep → deterministic (the existing helper calls real time.sleep). Mirrors Playwright expect.poll.
• Matcher factories: to_equal, to_contain, to_be_greater_than, to_match_regex, to_be_truthy, to_be_stable(n) (matches once the value repeats n times).
• AC_expect_poll re-runs a nested action (e.g. ["AC_get_clipboard"]) until a key of its result matches op (truthy/equals/contains/gt/regex) vs expected — usable from JSON/MCP/builder.
• Pure-stdlib; fully headless-testable (fake clock advances only on sleep). Wired through all 5 layers + headless test + EN/Zh docs + WHATS_NEW. Qt-free.

[codacy-production]

Not up to standards ⛔

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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