feat(common): add deferred poll timeout support

[arunsingh]

Which issue does this PR address?

Closes #3470

Rationale

PollMessages needs a backward-compatible way for clients to request a bounded wait when no messages are available. Immediate polling remains unchanged for existing clients and for a zero timeout.

What changed?

Empty PollMessages requests can now carry a trailing wait_timeout_us field; legacy requests decode it as zero, while partial trailing fields are rejected. The common, SDK, consumer-group, simulator, and HTTP-zero paths carry the value through the current tree.

This is a clean rebuild after closed PR #3605. The active core/server path currently rejects non-zero waits with typed FeatureUnavailable until a safe waiter/notifier implementation is designed. No core/server-ng, legacy server, benchmark markdown, or runbook files are included.

Local Execution

• cargo fmt --all — passed
• cargo clippy --all-targets --all-features -- -D warnings — passed
• cargo test -p iggy_binary_protocol poll_messages — 15 passed
• cargo test -p iggy_common wait_timeout — 2 passed
• cargo check -p iggy -p server -p simulator — passed
• cargo check -p integration --tests — passed
• cargo machete — passed
• cargo sort --workspace — passed; no changes needed
• typos — passed
• ./scripts/ci/license-headers.sh --check — passed with HawkEye 7
• git diff --check — passed
• Pre-commit hooks — not run; prek is not installed in this environment

cargo build --workspace was attempted but could not link in this x86_64-targeted macOS environment because the installed Homebrew xz and hwloc libraries are arm64. Full local cargo test is not claimed. Fresh GitHub CI run 32720521140 passed all 74 jobs after the rebase onto current master.

AI Usage

AI was used for code review, and test/CI orchestration. The changed code was reviewed and verified with the local checks above and GitHub CI; I can explain every line of the code if asked.

[codecov]

Codecov Report

❌ Patch coverage is 97.61905% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.73%. Comparing base (a65f177) to head (d86e92b).

Files with missing lines	Patch %	Lines
core/common/src/traits/binary_impls/messages.rs	92.30%	2 Missing ⚠️
core/server/src/dispatch.rs	96.42%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3948      +/-   ##
============================================
- Coverage     83.93%   83.73%   -0.20%     
  Complexity     1358     1358              
============================================
  Files          1213     1214       +1     
  Lines        168441   168258     -183     
  Branches     135999   135941      -58     
============================================
- Hits         141373   140884     -489     
- Misses        23389    23557     +168     
- Partials       3679     3817     +138     

Components	Coverage Δ
Rust Core	84.56% <97.61%> (-0.16%)	⬇️
Java SDK	66.67% <ø> (ø)
C# SDK	74.97% <ø> (-1.56%)	⬇️
Python SDK	90.13% <ø> (ø)
PHP SDK	84.48% <ø> (ø)
Node SDK	95.90% <ø> (ø)
Go SDK	68.29% <ø> (ø)

Files with missing lines	Coverage Δ
...ry_protocol/src/requests/messages/poll_messages.rs	100.00% <100.00%> (ø)
core/common/src/traits/message_client.rs	100.00% <100.00%> (ø)
...e/sdk/src/client_wrappers/binary_message_client.rs	100.00% <100.00%> (ø)
core/sdk/src/clients/binary_message.rs	100.00% <100.00%> (ø)
core/server/src/http/wire.rs	95.08% <100.00%> (+0.01%)	⬆️
core/simulator/src/client.rs	65.96% <100.00%> (+0.07%)	⬆️
core/server/src/dispatch.rs	89.55% <96.42%> (+0.05%)	⬆️
core/common/src/traits/binary_impls/messages.rs	84.55% <92.30%> (+0.62%)	⬆️

... and 73 files with indirect coverage changes

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[arunsingh]

Thanks, for reviewing earlier old PR #3605. I reopened this cleanly against current master and moved the implementation to the active core/server path. This is trailing PR to #3605, I kept the markdown/runbook artifact out of the new PR.