[Feature] Code Import Runtime Hardening #234

Summary

Harden the code-import runtime for real-world repositories: prune hidden and heavyweight artifact trees before traversal, support a repo-local .specfact/.specfactignore, warn when imports encounter unusually large artifact volumes, and ensure packaged project-runtime templates are shipped and resolvable at runtime.

Scope

• packages/specfact-project — import traversal policy, warning surfaces, live ETA/progress calculation, generator template packaging
• packages/specfact-codebase — import command surface alignment for the shared runtime policy

Parent Epic

Part of #162 — [Epic] specfact code

Changes

• #235 — Codebase import runtime hardening