feat(graph): add production graph metric lifecycle and queries

[ajroetker]

What changed

• adds durable degree, PageRank, eigenvector, and compatible HITS metric lifecycles over graph indexes
• runs resumable coordinator and worker/worker-pool roles through std.Io and the database backend runtime, with durable owner leases, page leases, attempt fencing, retries, publish verification, cleanup, and restart recovery
• exposes direct top-k graph metric reads, traversal projection/order/filtering, freshness controls, score reranking, status/profile details, and fail-closed hosted fan-in
• adds internal maintenance operations, runtime status/telemetry, a user-facing maintenance command plus hidden supervisor child alias, and production-shaped process gates
• extends OpenAPI and the Go, TypeScript, Python, and Zig client/contracts, including ergonomic direct graph-metric SDK request fields
• ports the comprehensive PageRank design and operations guide from the combined graph work

Architecture and UX

• production graph maintenance does not spawn raw OS threads; it uses backend_runtime.io_impl, std.Io futures, mutexes, conditions, and bounded runtime lanes
• the process harness uses the same opaque API-kernel + httpx composition as production
• the primary database backend remains LSM by default; graph metrics do not implicitly enable or depend on LMDB
• graph JSON tests use structural lib/json assertions rather than serialization-order substrings
• direct graph-metric, rerank, pruner, and mixed queries use the general read path so post-processing and admission behavior remain correct
• publication is atomic and fail-closed: missing, malformed, or non-finite final ranks fail the durable page instead of publishing zero-valued or partial PageRank, eigenvector, or paired HITS generations

Validation

• focused missing-final-rank PageRank recovery regression — 1/1 passed, no leaks
• focused missing-paired-HITS-rank recovery regression — 1/1 passed, no leaks
• zig build graph-metric-unit-test -fincremental --summary all — 74/74 passed, no leaks
• zig build graph-metric-integration-test -fincremental --summary all — 94/94 passed, no leaks
• zig build graph-metric-process-test -fincremental --summary all — 25/25 build steps; all promotion/failover proof floors met
• graph metric command, supervisor, and smoke gates passed
• zig build antfly-main-test -fincremental --summary all — 8/8 passed, no leaks
• make zig-generated-check — OpenAPI/MCP, Snowball, SQL grammar, C ABI header, and TLS checks passed
• Go SDK generation, tests, vet, and race detector passed
• TypeScript SDK generation/typecheck passed; 155 tests passed, 1 skipped
• Python SDK generation, Ruff, Pyright, and 23 tests passed
• git diff --check

Notes

• merged current main and regenerated all affected clients; the PR is conflict-free at the pushed head
• kept as draft for review because this intentionally expands the original kernel-only PR into the comprehensive graph-metrics production slice