fix: harden client telemetry (#587, #588)

[yhmo]

• Treat ttl_seconds as an ignored push_config field (fix: treat ttl_seconds as an ignored push_config field #587)
• Harden client telemetry control flow: make very large heartbeat intervals safe and cancellable across platforms, fence command batches across telemetry transport rebinding, canonicalize ACK IDs, wake the unsupported backoff on channel replacement, and bound show_errors truncation including UTF-8 payloads (fix: harden client telemetry control flow #588)

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: yhmo

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🟢 Approval recommended

The changes are well-scoped, appear correctness-focused, and are backed by targeted unit tests that exercise the newly hardened control-flow paths.

Pull request overview

This PR hardens the SDK’s client-side telemetry pipeline by making heartbeat scheduling and command processing more robust (especially under extreme intervals and transport rebinding), while also relaxing client validation for server-only push fields.

Changes:

• Clamp and chunk very large heartbeat intervals to keep waits cancellable and safe across platforms.
• Fence command execution across telemetry transport rebinding and canonicalize ACK correlation IDs.
• Improve show_errors payload bounding (including UTF-8-safe truncation) and treat ttl_seconds as an ignored push_config field.

File summaries

File	Description
src/impl/ClientTelemetry.cpp	Implements heartbeat interval clamping/chunked waits, channel-rebind fencing, ACK ID canonicalization, unsupported-backoff wakeup on channel replacement, and bounded UTF-8-safe show_errors truncation; removes ttl_seconds validation from push_config.
test/ut/TestClientTelemetry.cpp	Adds/updates unit tests covering max heartbeat intervals, ACK ID behavior, generation-switch fencing, backoff interruption on rebind, immediate probe on replacement during in-flight heartbeat, show_errors truncation bounds (incl. UTF-8), and ttl_seconds ignored behavior.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Lite

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[codecov]

Codecov Report

❌ Patch coverage is 87.00000% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.02%. Comparing base (a0592aa) to head (128339d).
⚠️ Report is 158 commits behind head on master.

Files with missing lines	Patch %	Lines
src/impl/ClientTelemetry.cpp	87.00%	39 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #601       +/-   ##
===========================================
+ Coverage   53.47%   88.02%   +34.55%     
===========================================
  Files          52      389      +337     
  Lines        4432    16580    +12148     
  Branches        0     1834     +1834     
===========================================
+ Hits         2370    14595    +12225     
+ Misses       2062     1985       -77     

Files with missing lines	Coverage Δ
src/impl/ClientTelemetry.cpp	85.09% <87.00%> (ø)

... and 405 files with indirect coverage changes

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