feat: support managed resume hints

[alupao]

What changed

• add an optional CLAUDEX_RESUME_HINT environment variable for launchers that own session recovery
• replace Claude Code's native claude --resume ... line with that managed command in interactive Unix sessions
• suppress Claudex's duplicate resume footer only when replacement succeeds
• preserve partial resume output across PTY read timeouts and keep default behavior unchanged when the variable is absent or invalid
• document the integration in English and Chinese

Why

Managed launchers such as Orichum expose their own logical session identifiers and recovery command. Printing both the native Claude command and a second wrapper-specific command is noisy and can encourage users to bypass the managed runtime on resume.

Closes #12.

Validation

• cargo fmt --check
• cargo clippy -- -D warnings
• cargo check
• cargo test (348 unit tests and 1 integration test passed)