feat: install strict backend-local PhysicalPlan profile

[zzylol]

Stack order

1. feat(query): compile generic post-ASAP DAG bindings #494 — strict generic QueryPlan DAG compiler/runtime
2. feat: add backend-local Remote Write foundation #493 — backend-local Prometheus Remote Write foundation
3. feat: install strict backend-local PhysicalPlan profile #495 (this PR) — strict PhysicalPlan startup/install integration

This PR contains only the strict integration delta over #493.

Scope

This is a physical-plan boot/backend-local ingest phase, not all six compatibility phases. It adds PrometheusRemoteWriteV1 to PrecomputePlan, removes compatibility-profile streaming-config authority, validates a complete JSON PhysicalPlan artifact before startup, reuses validation for staged installs and atomic activation, disables partial config/BackendPlan handles, snapshots one plan per write, scopes deduplication to plan identity/version, gates readiness, and relies on #494 authoritative QueryPlan DAG execution with exact fallback on capability miss.

Verification

• formatting and data-plane binary check pass
• data-plane library: 959 passed with one test thread
• control-plane library: 630 passed
• binary/profile: 3 passed
• no ignored Rust E2Es
• Collector-free HTTP contract posts real Snappy/protobuf Remote Write against an active backend-local plan and verifies 204, counters, readiness, and invalid-encoding rejection

The default parallel suite exposed two pre-existing global-state races; both pass individually and the complete single-threaded suite passes.

Explicit blockers / non-goals

1. Canonical startup compilation still needs stable serializable QueryWorkload/DataWorkload contracts and a backend-only PhysicalCompiler target; this phase consumes an offline artifact.
2. A full Remote Write → closed window → QueryPlan warm result → coverage fallback process E2E needs a canonical generated artifact fixture. This PR covers the real Collector-free ingest/readiness boundary; feat(query): compile generic post-ASAP DAG bindings #494 covers bound DAG execution and coverage separately.
3. Existing exact rate/increase, range-step, and production sketch-result blockers remain out of scope.

This PR does not claim the complete compatibility profile.