[Juliusolsson05]

The always-on monitor needs a bounded, content-minimized foundation before production collection is enabled. This adds a finite operation vocabulary, strict renderer record validation, queues bounded by count and conservative wire bytes, and mergeable latency histograms that retain sample weighting and explicitly represent overflow.

A synthetic producer benchmark measures validation/queue/histogram cost without reading user data or claiming whole-application overhead. The detailed rollout plan is included as the first branch commit. Production collection and UI are unchanged in this first stage.

Fixes #948
Refs #944

Validation:

• 21 focused tests passed, including nested/private-field rejection, oversized batches, sustained queue overload, and weighted latency rollups.
• Strict standalone TypeScript checking passed for the production shared modules.
• Synthetic arm64 / Node 25.5.0 benchmark: 100,000 operations; p99 2.042 µs; 61.605 ms process CPU. These are producer-only measurements, not the planned packaged-app overhead qualification.
• Full repository CI and two independent Agent Code orchestration reviews will be recorded before merge.

The remaining collector, product UI, incident, durable history, and profiling stages stay open under #944. Packaged-app/Intel/long soak validation has not been performed at this foundation stage.

Review: two independent Agent Code orchestration agents reviewed this PR. Sparse histogram buckets, fabricated empty-window totals, and impossible bucket-weighted sums were corrected with regressions; both reviewers verified the final head with no further findings. No baseline collection or UI is enabled by this foundation PR alone.

CI passed on head 5cda062 (quality gate and minimum-Node fixture gate).