fix(#3453): resolve concurrency, leak, and panic issues from code audit

[HarshMehta112]

Fixes #3453

Addresses six source-grounded findings around concurrency correctness, memory/goroutine
leaks, and panic-based failure handling. Each fix is narrowly scoped with focused tests.

1. RoundRobin selection now atomic under concurrency

cluster/loadbalance/roundrobin/loadbalance.go
The weighted-round-robin select+update sequence was only per-field atomic, so concurrent
callers could observe each other's intermediate currentWeight and skew distribution.
Added a per-key sync.Mutex on cachedInvokers so the full select+update transaction is
serialized per service+method (contention bounded to the same key).

2. Getty server no longer panics on config errors

remoting/getty/getty_server.go
Replaced panic(err) in config marshal/unmarshal, CheckValidity(), and newSession()
with structured error logging / error returns. Added safeYAMLMarshal to recover the
panic yaml.v3 raises on unmarshalable types (channels, funcs) and surface it as an error.
Malformed protocol config no longer escalates to process-level failure.

3. Graceful shutdown result publication hardened

graceful_shutdown/shutdown.go
Added shutdownResultMu guarding all reads/writes of the package-level shutdownResult,
removing reliance on subtle ordering assumptions between the background shutdown goroutine
and concurrent Shutdown() readers.

4. TPS limiter cache is now bounded

filter/tps/limiter/method_service.go
The limiter map grew for process lifetime as distinct service+method combos accumulated.
Wrapped each strategy in a tpsLimitEntry tracking last-access time, switched to sync.Map,
and added a singleton background runCleanup goroutine that evicts entries idle past a TTL.

5. Script-router JS runtime no longer leaks cross-request state

cluster/router/script/instance/js_instance.go
Pooled goja.Runtime instances were never returned to the pool, and request/script globals
survived reuse. Added defer reset()+Put() in Run(). reset() snapshots the built-in
global keys at construction and deletes every global outside that set — clearing both request
bindings and user-script-defined globals while preserving built-ins.

6. Forking cluster cancels losing parallel branches

cluster/cluster/forking/cluster_invoker.go
Losing parallel invocations ran to completion after the winner returned, wasting downstream
work. Derived a cancelable forkCtx; defer cancel() stops sibling requests as soon as the
first accepted result wins.

Tests

• TestRoundRobinByWeightConcurrent — 50 goroutines × 30 selections, race-clean
• TestInitServerDoesNotPanicOnUnmarshalableParams — channel in Params no longer panics
• TestShutdownResultConsistentUnderConcurrentReaders, TestShutdownPanicSetsResultError
• TestTpsLimitEntryUpdatesLastAccess, TestTpsLimiterStaleEntryEviction
• TestJsInstanceResetClearsBindings (incl. user-defined global), TestJsInstanceRunReturnsRuntimeToPool
• TestForkingInvokeCancelsLosingBranches — loser branch ctx canceled after winner succeeds

All 74 tests across the 6 packages pass; go vet and gofmt clean.

Scope

Covers audit items 1–6 only. Item 7 (broader panic/fatal policy audit) is left for follow-up
PRs per the issue's suggested slicing. Items A/B/C are already fixed upstream.

Checklist

• I confirm the target branch is develop
• Code has passed local testing
• I have added tests that prove my fix is effective or that my feature works

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.75758% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.09%. Comparing base (8b5bbcf) to head (5cfc4a8).
⚠️ Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
filter/tps/limiter/method_service.go	70.83%	6 Missing and 1 partial ⚠️
remoting/getty/getty_server.go	61.53%	5 Missing ⚠️
cluster/router/script/instance/js_instance.go	75.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3461      +/-   ##
===========================================
+ Coverage    53.57%   54.09%   +0.52%     
===========================================
  Files          460      461       +1     
  Lines        35182    35530     +348     
===========================================
+ Hits         18847    19220     +373     
+ Misses       14857    14791      -66     
- Partials      1478     1519      +41     

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[Alanxtl]

1. comment in the issue before summitting pr
2. split this pr into 6 small prs, this one is too large to review