style(networkstream): trim comments, keeping the reasoning in the feature doc (SUB-7786)

The comments had grown to restate measurements, production numbers, calibration
tables and history inline -- all of which is already in
docs/features/network-stream-process-attribution.md, where it belongs and can be
kept current. Inline, it just made the code harder to read.

Kept only what a reader needs at that spot: the invariants that cause a bug if
violated (never scale StartTimeNs, never write to a shared tree node, don't
replace the copier with DeepCopy, take the ref before the mutex) and one pointer
to the doc. 419 -> 287 comment lines, no behaviour change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Signed-off-by: Alon <alon@armosec.io>