starknet_transaction_prover: document existing logging, request ids and health probe in README

[avi-starkware]

Adds a top-level Observability section to the README covering the
HTTP-only side endpoints (/health, /metrics), the metric names and
label sets, request-id propagation rules, the per-request log shape, the
startup banner, and the graceful-shutdown / panic-hook contract.

Updates the Environment variables table with LOG_FORMAT and
HEALTH_MAX_SATURATED_MS, the JSON config table with
health_max_saturated_ms, and the Logging subsection with the JSON
format option and URL redaction note.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[cursor]

PR Summary

Low Risk
Documentation-only README changes with no runtime or configuration behavior changes in this diff.

Overview
README-only updates for starknet_transaction_prover: operators get clearer docs for how the service behaves under load and what shows up in logs.

The configuration tables now describe a FIFO queue beyond worker slots: MAX_CONCURRENT_REQUESTS is framed as parallel proving workers, with new MAX_QUEUED_REQUESTS and QUEUE_WAIT_TIMEOUT_MILLIS (and matching JSON config fields) explaining when clients see -32005 vs waiting.

Logging documents LOG_FORMAT (text vs json), JSON log shape, and URL redaction in startup/override messages so credentials in RPC URLs are not logged.

A new Observability section covers GET /health (unauthenticated, early in the router stack), x-request-id propagation and validation (including OHTTP outer vs inner ids), and the per-request event="http_request" structured log line (with probe and body-privacy notes). The API reference now points at /health alongside JSON-RPC.

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[reviewable-StarkWare]

This change is 

[avi-starkware]

• starknet_transaction_prover: log resolved config at startup (secrets redacted) #14684
• starknet_transaction_prover: origin-level breadcrumbs for validation errors #14172
• starknet_transaction_prover: /health returns 503 when service is saturated #14171
• starknet_transaction_prover: track saturation and queue depth on the request path #15027
• starknet_transaction_prover: bump prover_panics_total on panic hook fire #14170
• starknet_transaction_prover: HTTP request count + latency + in-flight metrics #14169
• starknet_transaction_prover: proving-job duration + outcome metrics #14168
• starknet_transaction_prover: Prometheus /metrics endpoint with build_info #14167
• starknet_transaction_prover: extract the TLS accept loop and test its drain #15049
• starknet_transaction_prover: graceful shutdown on SIGTERM/SIGINT #15026
• starknet_transaction_prover: global panic hook with structured log #14166
• starknet_transaction_prover: document existing logging, request ids and health probe in README #14203 👈 (View in Graphite)
• main-v0.14.4

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[einat-starkware]

@einat-starkware reviewed 1 file and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Yoni-Starkware).