Configure HTTP/2 timeouts via environment

[wyeth93]

Summary

• add strict PULSING_HTTP2_* timeout environment variables across ActorSystem, Connect, Python, and RustPython entry points
• preserve explicit Http2Config precedence over environment-derived defaults
• enforce a hard streaming deadline and surface typed RequestTimeout errors
• document defaults, validation, precedence, and scope in English and Chinese
• add regression coverage for environment parsing and silent streaming timeouts

Why

HTTP/2 timeouts were hard-coded, and the stream timeout was only checked when frames arrived. A silent stream could therefore remain open indefinitely and terminate without a typed timeout error.

Impact

Operators can tune remote HTTP/2 transport timeouts per process without code changes. Existing defaults remain 5s / 30s / 300s when variables are unset. Invalid or zero values fail configuration loading. Local actor asks and server handler deadlines are unchanged.

Validation

• cargo fmt --all -- --check
• cargo test -p pulsing-actor
• cargo check --workspace
• cargo clippy -p pulsing-actor --all-targets -- -D warnings
• git diff --check

[codecov-commenter]

Codecov Report

❌ Patch coverage is 64.92891% with 74 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/pulsing-actor/src/transport/http2/client.rs	46.55%	31 Missing ⚠️
crates/pulsing-actor/src/system/config.rs	14.28%	18 Missing ⚠️
crates/pulsing-actor/src/transport/http2/config.rs	91.74%	9 Missing ⚠️
crates/pulsing-actor/src/connect/mod.rs	50.00%	7 Missing ⚠️
crates/pulsing-rpymod/src/bindings/message.rs	0.00%	5 Missing ⚠️
crates/pulsing-rpymod/src/runtime.rs	0.00%	4 Missing ⚠️

Files with missing lines	Coverage Δ
crates/pulsing-rpymod/src/runtime.rs	0.00% <0.00%> (ø)
crates/pulsing-rpymod/src/bindings/message.rs	0.00% <0.00%> (ø)
crates/pulsing-actor/src/connect/mod.rs	25.66% <50.00%> (+3.66%)	⬆️
crates/pulsing-actor/src/transport/http2/config.rs	83.21% <91.74%> (+7.51%)	⬆️
crates/pulsing-actor/src/system/config.rs	81.08% <14.28%> (-2.70%)	⬇️
crates/pulsing-actor/src/transport/http2/client.rs	59.74% <46.55%> (+3.68%)	⬆️

... and 5 files with indirect coverage changes

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