[codex] Add manual timer API for tests

[Bathtor]

What changed

• add a manually-driven timer API for deterministic tests
• expose the timer-backed current time through KompactSystem::now() and SystemHandle::now()
• add install_manual_timer and a regression test that proves timers do not fire until explicitly advanced
• update the timer dependency requirement to the 1.4 series needed for the manual timer API

Why

The vendored kompact-0.11.3 changes add support for deterministic timer-driven tests. This ports that behaviour into the workspace layout used in the upstream repository.

Validation

• cargo test -p kompact installed_manual_timer_requires_explicit_advance --quiet

[Bathtor]

@codex review

[Bathtor]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Nice work!

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