Make context the node retrieval field

[chailandau]

Category: improvement
User Impact: Agents can use clearer context frontmatter to decide which brand guidance applies without silently losing retrieval coverage.
Problem: Node retrieval currently reads description, so authors cannot rename the field to context without producing blank gather menus. A fingerprint-only migration would validate successfully while quietly making nodes undiscoverable.
Solution: Make context canonical throughout schema, catalog, gather, pull, review, serialization, validation, docs, and repo-owned packages. Keep description as a deprecated compatibility alias for one release, warn on its use, and serialize it back as context so existing packages remain retrievable during migration.

Validation:

• pnpm check: passed
• pnpm exec vitest run packages/ghost/test packages/context-control/test: passed, 180 passed and 1 skipped
• pnpm test: 203 passed and 1 skipped; one unrelated local environment failure in steering-control because process.execPath contains a space and ghostBin.split() attempts to execute /Users/chai/Library/Application
• ghost validate for apps/docs/.ghost and packages/vessel-light/.ghost: passed with no warnings
• ghost validate for packages/vessel-react/.ghost: passed with its existing cover-undeclared warning

Changeset: added as a minor release because this introduces the public context retrieval capability.

ghost Review:

• ghost check --base main: not available in the current CLI; deterministic package and repository checks ran through pnpm check
• ghost review --base main --include-memory: not available in the current CLI shape; review packet behavior is covered by the Ghost test suite

File changes

.changeset/node-context-retrieval.md
Records the new public node retrieval capability as a minor release.

packages/ghost/src/ghost-core/node/
Adds canonical context schema and types, accepts deprecated description, and migrates the alias during serialization.

packages/ghost/src/ghost-core/catalog/
Resolves node context with canonical precedence and emits it through gather menu entries while retaining transition aliases.

packages/ghost/src/embed/ and packages/ghost/src/commands/
Uses context in gather selection instructions, coverage, menu output, and pull packets; keeps deprecated JSON compatibility fields for one release.

packages/ghost/src/scan/fingerprint-package-lint.ts
Warns when context is missing and when deprecated description frontmatter needs migration.

packages/ghost/src/review/
Carries context through review baselines and material-backed review nodes.

packages/ghost/src/init-payloads/, packages/vessel-light/.ghost/, packages/vessel-react/{.ghost,fingerprint}/, and apps/docs/.ghost/
Migrates repo-owned node frontmatter to context; check documents retain their separate description schema.

packages/ghost/src/skill-bundle/, README.md, and docs/purposes.md
Documents context as the retrieval payload and the one-release compatibility window.

packages/context-control/
Updates the retrieval benchmark, model prompt, and viewer to evaluate node context.

apps/docs/src/
Updates public examples and gather demonstrations to show context.

packages/ghost/test/
Covers canonical context, deprecated alias reads, precedence, migration serialization, lint warnings, coverage, gather, pull, and embed output.

Screenshots/Demos: N/A; this changes framework terminology and output contracts without changing the rendered design.