Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@agents/grpc/src/grpc_agent.cc`:
- Around line 1761-1763: PopulateReconfigureEvent currently omits the
traceSampleRate field when building the outgoing reconfigure event body; update
PopulateReconfigureEvent to set body.traceSampleRate from the internal config so
the outgoing event mirrors inbound updates (i.e., when you previously read
body.tracesamplerate() on incoming updates, ensure PopulateReconfigureEvent
calls the corresponding setter to populate body.traceSampleRate in the event).
Locate the PopulateReconfigureEvent function in grpc_agent.cc and add the
traceSampleRate assignment using the same source/field used for other mapped
settings so reconfigure responses include traceSampleRate.

In `@lib/nsolid.js`:
- Around line 1144-1154: The parseTraceSampleRate function currently coerces
unintended types via unary +; update parseTraceSampleRate to only accept inputs
that are typeof 'number' or 'string', explicitly reject booleans and other
types, trim string inputs and return undefined for empty/whitespace-only
strings, then convert the trimmed numeric string (or the number input) to a
numeric value and validate with NumberIsFinite and range checks (>=0 && <=1);
ensure the function returns undefined for invalid types, whitespace-only
strings, NaN, non-finite numbers, or values outside the 0–1 range while
returning the numeric rate for valid inputs.

In `@test/parallel/test-nsolid-config-trace-sample-rate-env.js`:
- Around line 15-18: The test currently spreads process.env into the child env
(env: {...process.env, ...envVars}), which can leak ambient NSOLID_* variables
and make the test nondeterministic; update the env construction in
test/parallel/test-nsolid-config-trace-sample-rate-env.js to explicitly filter
out any keys starting with "NSOLID_" (e.g., build a filteredEnv =
Object.fromEntries(Object.entries(process.env).filter(([k]) =>
!k.startsWith('NSOLID_'))) and then use env: { ...filteredEnv, ...envVars } so
the child process is isolated from ambient NSOLID_* variables while still
allowing envVars to override.

---

Nitpick comments:
In `@test/agents/test-grpc-reconfigure.mjs`:
- Around line 171-208: Update the test "should preserve previous traceSampleRate
for invalid values" to include NaN and Infinity cases: add Number.NaN,
Number.POSITIVE_INFINITY and Number.NEGATIVE_INFINITY (or +/-Infinity) to the
invalidRates array used with grpcServer.reconfigure and client.config assertions
so grpcServer.reconfigure(agentId, { traceSampleRate: invalidRate }) is
exercised for NaN/Infinity and the existing assert.strictEqual checks that
nsolidConfig.traceSampleRate remained 0.4 still apply.

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/nsolid/nsolid_api.cc`:
- Around line 1251-1256: The current code checks curr for "traceSampleRate" and
calls update_tracing_sample_rate even when the incoming config didn't include
it; change the condition to check config.find("traceSampleRate") (like
promiseTracking does) and only call update_tracing_sample_rate when the incoming
config contains that key, so you don't propagate RunCommand to all EnvInsts for
unrelated updates; alternatively, if you prefer keeping the check on curr, add
an early-return/short-circuit inside update_tracing_sample_rate to detect and
skip re-propagation when the effective sample rate value hasn't changed.