fix: oneway shm calls, mem-ring unstuck notify and misc review fixes

[lirenjie95]

• r2g: emit a real Go handler for no-return #[mem]/#[shm] functions instead of an ack-only stub that silently discarded every request; box the parameters like the async path and free them on the DROP ack so Go never reads freed request memory, with the unsafe contract for reference parameters documented
• mem-ring: the Go reader now clears the stuck flag and notifies the unstuck fd on pop so writers parked on a full ring flush their pending items (mirrors the Rust ReadQueue::pop); close the stuck-handshake lost-wakeup window by redelivering directly after mark_stuck; exit the Rust handlers when the peer closes the notification socket instead of busy-spinning; reject zero-sized rings; drop items still buffered on queue drop and wake parked push_with_awaiter futures when the write queue is dropped
• asmcall: reserve the Win64 32-byte shadow space around both call paths in amd64.s; document that the in-place P-variants do not normalize the stack pointer on amd64 (arm64 does), so their callees must tolerate 8-byte alignment (EN and ZH READMEs)
• g2r: replace the dyn Any round-trip for response storage with typed c_{trait}_{fn}_drop entries per function so the payload destructors run and the allocation is freed with the correct layout; keep user parameter objects alive across the FFI call; sync the committed generated Go files
• future: require Exec: Send/Sync in the manual Send/Sync impls of ResponseFuture
• macro/codegen robustness: reject queue_size = 0 and malformed or unknown #[rust2go::r2g] attributes with spanned errors; reject cyclic struct definitions, u128/i128 and char with clear diagnostics; validate parameter names against Go keywords, raw identifiers and a flat, deliberately conservative list of the identifiers the generated bindings reference, plus per-function conversion-local name pairs; support zero-parameter trait functions (ToRef/FromRef for the unit type); pass the sync-ret slot as a mutable pointer
• generator: import runtime, cgocall and asmcall only when the generated code actually references them
• docs: document U+FFFD replacement for non-UTF-8 Go strings, the mem-ring drop quiescence contract, and the asmcall alignment contract
• tests: exercise oneway mem calls end to end in the test crate and assert delivery through a Go-side invocation counter, plus regression tests for the mem-ring fixes and the new diagnostics

[codecov-commenter]

Codecov Report

❌ Patch coverage is 89.81670% with 50 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.35%. Comparing base (4ba6b18) to head (7baee66).

Files with missing lines	Patch %	Lines
mem-ring/src/queue.rs	64.64%	35 Missing ⚠️
rust2go-macro/src/lib.rs	92.18%	5 Missing ⚠️
rust2go-common/src/r2g/emit_go.rs	86.66%	4 Missing ⚠️
rust2go-common/src/g2r/mod.rs	97.14%	2 Missing ⚠️
mem-ring/src/eventfd.rs	80.00%	1 Missing ⚠️
rust2go-common/src/g2r/emit_c.rs	88.88%	1 Missing ⚠️
rust2go-common/src/r2g/emit_rust.rs	83.33%	1 Missing ⚠️
rust2go-convert/src/convert.rs	94.11%	1 Missing ⚠️

❌ Your project status has failed because the head coverage (96.35%) is below the target coverage (97.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #199      +/-   ##
==========================================
- Coverage   97.02%   96.35%   -0.67%     
==========================================
  Files          24       23       -1     
  Lines        4098     4530     +432     
==========================================
+ Hits         3976     4365     +389     
- Misses        122      165      +43     

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