Feature Pack H: codebase knowledge graph (Graphify) for generated projects

Came out of an ideation session, not a scoped request.

Build the Graphify pack described in `README.md` (Feature Pack H) and offered as an `gonext init` prompt in `roadmap.md`: a Tree-sitter AST and schema graph over a generated project, emitting `graph.json`, `GRAPH_REPORT.md` and an interactive `graph.html`, driven by a `make graphify` target, so AI coding agents can traverse the project's dependencies without loading the whole tree.

Scope is deliberately limited to **generated projects only**. Running it over the gonext repo itself was considered and dropped: this repo is small, `CLAUDE.md` already describes its layout better than a graph would, and its genuinely confusing part — the `templates/` ↔ `golden/` relationship and the `[PROJECT-NAME]` token — is exactly what an AST parser handles badly, since `templates/` does not compile standalone.

Read Feature Pack H in README.md and the corresponding gonext init prompt in roadmap.md first. Define the generated-project scope and investigate the existing make targets before planning the Tree-sitter and schema-graph work. Done means make graphify emits graph.json, GRAPH_REPORT.md, and an interactive graph.html for a generated project.

Written by the indexing model from the issue text.