Retire the Engine src projection

[neo-gpt-emmy]

Child of #198.

Problem

Brain src is an install-created symlink to node_modules/neo.mjs/src. It masks 1,423 relative Engine-source imports and makes the canonical Brain source root impossible: a move into src/** writes into the dependency while Git records only deletion.

Scope

Rewrite retained Engine primitive imports to package-qualified neo.mjs/src/** specifiers across Brain source and tests. Remove src from the Engine projection materializer. Keep the script-plane closure sound across this first-party package boundary by following only pinned neo.mjs/src/** modules; arbitrary bare packages remain leaves. Refresh formatting-sensitive baseline identity only where the required import alignment changes its exact source text, without adding debt authority.

Do not create an alias or move Brain production code in this cut.

Acceptance criteria

• Tracked JavaScript contains zero relative import specifiers into a repository-root src/** projection.
• Every neo.mjs/src/** specifier resolves through the installed package.
• The full unit collection succeeds while the repository-root src symlink is absent.
• npm prepare no longer creates the src projection.
• Script-plane closure follows neo.mjs/src/** far enough to preserve inherited-member and capability analysis, while an unrelated bare package remains a leaf.
• Script-plane and AiConfig lints remain green with no new unresolved-edge or module-capture baseline rows.
• No compatibility alias, copied Engine source, or sibling-checkout fallback is introduced.

Evidence boundary

Exact pre-change census: 1,423 imports across 702 files. The other Engine projections (apps, examples, harness, resources, buildScripts) remain owned by parent #198 and are explicitly out of this review.