Rename @codeassembly/kb-core to @codeassembly/kb

[williamthorsen]

Problem

Before the package is ever published, its name and the directory it lives in should be corrected — both become permanent the instant a version ships. -core conventionally signals "not directly usable without a binding," but this package is consumed directly and has no binding family, so the suffix misdescribes it. Separately, the registry loader currently owns the KbConfig/loadKbConfig names that the store-level config loader (added in the feature ticket) should hold.

Context

• Pre-publish, so all renames are free. The directory, package name, every workspace:* consumer, every import, and the skill-helper bundler references must move together.
• The ~/.agents/kb.yaml loader (loadKbConfig/tryLoadKbConfig/KbConfig/KbConfigEntry) loads a registry of KBs, not a single store's config. Renaming it to registry-specific names frees the KbConfig/loadKbConfig names for the store's .kb/config.yaml.
• Isolated as a rename-only change so it carries zero behavior risk and keeps the feature ticket's diff purely about new behavior.

Proposed solution

Rename the package @codeassembly/kb-core → @codeassembly/kb and the directory packages/kb-core → packages/kb, updating every workspace:* consumer, import, and skill-bundler reference. Rename the registry loader and its types to registry-specific names (loadKbRegistry / tryLoadKbRegistry / KbRegistry / KbRegistryEntry). No behavior changes.

Acceptance criteria

Must have

• Package renamed @codeassembly/kb-core → @codeassembly/kb (name and packages/kb directory).
• All workspace:* consumers, imports, and skill-helper bundler references updated; no kb-core references remain outside git history.
• Registry loader and types renamed to loadKbRegistry / tryLoadKbRegistry / KbRegistry / KbRegistryEntry.
• No behavior change; the existing test suite and skill-helper bundles pass with only identifier/import updates.
• User-facing docs/READMEs reflect the new name; no stale kb-core references.

Dependencies

• Blocks: Add a config-driven kb check CLI and library export #718 (the config-driven kb check feature).