bazel: model foundation and compiler-layer Rust libraries

[DecisionNerd]

Context

Implements step 3 of #1: model foundation and compiler-layer Rust libraries as real Bazel targets.

Work

• Map foundation/compiler-layer first-party crates from the ledger to Bazel labels.
• Reproduce edition, toolchain, features, lint-relevant flags, and build-script needs for those crates.
• Prove bazel build / bazel test (as applicable) for the mapped foundation set without Cargo shell-outs.
• Update the migration ledger with labels and residual gaps.

Acceptance criteria

Given #11 bootstrap is complete
When foundation and compiler-layer crates are modeled
Then those crates build under Bazel without shelling out to Cargo for ordinary compilation
And ledger rows for this slice list Bazel labels or explicit justified exceptions
And CI on Blacksmith can exercise the new targets

Out of scope

• Storage/exec/search/knowledge/API layers (bazel: model storage, execution, search, knowledge, and API libraries #9).
• Integration/BDD/resource graphs (bazel: model unit, integration, snapshot, BDD, CLI, and resource targets #8).
• PyO3/napi cdylibs (bazel: model PyO3 and napi-rs cdylibs plus packaging handoff #7).
• Mobile bindings.

Evidence

• PR + ledger update; exact-head applicable CI green.
• Ordinary AGENTS.md close.

Relationships

• Parent / blocks: M2 gate: implement #1 Bazel migration via sub-agents #2
• Blocked by: bazel: Bazelisk, Bzlmod, rules_rust bootstrap and drift checks #11
• Blocks: bazel: model storage, execution, search, knowledge, and API libraries #9
• Canonical spec: build: migrate CI builds and tests to Bazel with Blacksmith caching #1 (Implementation Sequence step 3)