refactor(core): simplify persistence boundaries - #43929

What

Simplify persistence and external-data boundaries by reusing canonical connection, filtering, normalization, and narrowing primitives. The refactor removes duplicated implementation while preserving every query, transaction, path, error, and provider-overlay behavior.

How

• Build the Workerd connection with the same Sqlite.makeConnection helper used by Bun and Node.
• Share Credential legacy-row filtering between all and list.
• Express Worktree create/remove results as direct boolean Effect transformations.
• Normalize ripgrep paths once across glob, find, and grep.
• Reuse one unknown-to-Error conversion across MCP promise boundaries.
• Use the canonical AI package isRecord guard for provider overlays.

Scope

Behavior-preserving Core cleanup only; no schema, migration, transaction, path policy, MCP recovery, provider merge, or public API changes.

Testing

• Persistence tests: 23 passed
• Ripgrep, MCP, and provider tests: 38 passed
• Simplify follow-up: bun run test test/ripgrep.test.ts (6 passed)
• bun typecheck from packages/core
• Push hook: bun turbo typecheck --concurrency=3 (40-package workspace)