Establish complete PostgreSQL request context across Graphile execution

[Zetazzz]

Summary

This combines planning items F02, F13, and F16 into one atomic request-context correction based on main.

• F02: @constructive-io/express-context now owns a canonical, complete pgSettings contract; pg-query-context applies all settings in one parameterized PostgreSQL round trip with transaction-local semantics.
• F13: Graphile i18n and LLM request-lane SQL now consume the existing complete Grafast request context and fail closed when it is missing. Bulk mutation SQL uses the native @dataplan/pg query-config contract.
• F16: PublicKeySignature derives a fresh anonymous execution context by copying the complete request settings and replacing only role with the configured anonymous role.
• The GraphQL server consumes req.constructive.pgSettings instead of reconstructing a second, incomplete settings object. Unauthenticated identity-bearing private headers remain inert until a separate authenticated internal-ingress boundary owns their translation.
• Ordered graphile.introspectionDependencySchemas are wired into the canonical request search_path alongside the resolved API schemas.

Planning: constructive-io/constructive-planning#1693

Ownership and security contract

packages/express-context owns the request facts and canonical builder. Every request gets a fresh object containing all supported security GUCs, with absent claims represented by empty strings, plus explicit role, request.id, transaction_read_only, search_path, and row_security values.

Trusted overrides are restricted to the declared security-GUC allowlist and reject accessors, symbols, arrays, nulls, non-string values, and PostgreSQL session controls such as role/search path/read-only/RLS. This PR does not translate caller-controlled identity headers into trusted claims; that requires the separately authenticated internal-ingress boundary excluded below.

postgres/pg-query-context owns application to PostgreSQL. Non-empty pooled context cannot be combined with skipTransaction; settings and callback failures roll back and release without replacing the original error. The direct algorithmic change is:

N per-setting SQL round trips -> 1 parameterized settings round trip

Ordinary Graphile lanes use the exact canonical object. The PublicKey lane creates a copy and changes only role; API/database/request identity, search path, RLS, read-only state, and empty-claim clearing are retained.

F13 package changes

• graphile-i18n: request withPgClient + complete pgSettings, native query-config execution, deterministic fail-closed behavior.
• graphile-llm: RAG and metering request lanes use the complete context; metadata queries use native query configs and preserve database errors while treating only absent optional module relations as unprovisioned.
• graphile-bulk-mutations: insert/upsert/update/delete callbacks use typed native PgClient queries.
• graphile-test: applies derivative settings in the existing test transaction and restores the primary request context. Root-mode fixtures default to the configured root connection user; explicit authRole, client context, and request role overrides remain effective. Real PostgreSQL regression tests cover root defaults, anonymous denial, explicit restricted roles, and restoration between requests.
• CI includes pg-query-context in the PostgreSQL test group. Refusal-context assertions verify both claims in the batched settings call and the transaction boundaries.

No storage plugins were changed.

Schema and behavior

• Public GraphQL SDL is unchanged.
• A real schema introspection contract verifies the three existing PublicKey mutation names, arguments, and return types.
• Signature verification remains behind its existing feature flag; this PR does not enable it or change that behavior.
• The active PublicKey signup/challenge paths use the common anonymous helper. Disabled verification/failure-recording behavior is intentionally not activated here.

Validation

Rebased onto main@7d28f718c049. Verified final head 10574e19f6df223edbdfc0f795cdba373c828901:

• Full CI: all 17 jobs passed
• Examples Integration: passed
• Frozen-lockfile installation and git diff --check passed.

Local verification:

• CJS/ESM builds for 10 affected or restored packages passed.
• Request-context regression checks across 7 packages: 12 suites / 109 tests passed. The 11 external Ollama tests were excluded only from this local run; the full remote AI job uses the real Ollama service.
• Additional debugging regression run: 26 suites / 336 tests passed across graphile-test, express-context, aggregates, connection filters, bulk mutations, and preset integration.
• CI package coverage check: all 108 test packages are assigned to a CI job.

Explicit exclusions

This does not include F01 runtime identity, F10 checkout sanitation, F14 storage snapshots/isolation, F07 SQL qualification, F08 cache ownership, F15 storage wiring, F17 build contracts, F18 admission or authenticated internal-ingress claims, scoped introspection behavior, build-state retirement, notification broker, pg-many-to-many, pnpm patches, Crystal/upstream changes, or performance-harness extensions.