feat(lens): clampLens — clamps into a lens's first layer (3.5.1)

[agreenspan]

Aron (2026-10-08): "get rid of those duplicate helpers for sure."

intoFirstLayer lived as a copy in template (@template/db/lens), its Kingdom and Tribe ports, and Zealot (@zealot/db, PR #2715). Its job is a lens-layer op: put clamps where they may read the whole schema — the first narrowing over the base lens (LENS.md: only layer 1's clamps read any relation; a later layer's only what its parent shows). It now lives here as clampLens(lens, clamps) (verb clamp, added to docs/VERBS.md; test/verbs.test.ts requires every export there).

• LensClamps = { root?: { where }, mapDefaults?: { [map]: { models: { [model]: { where?, sources? } } } } } — the copies' FirstLayerClamps, unchanged.
• Behaviour identical to the copies, except a sources entry is told apart from a bare Condition by the engine's own normalizeSource (the copies used their own key test), so the merge reads an entry exactly as the engine does; {} now throws the engine's invalid_source early.
• Tests: bare lens, AND with the first layer's where, later layers kept by reference, a clamp on a column a later layer hides validates only in layer 1, model-default wheres per map/model, source where AND + bare-Condition normalization + label/groupBy win, no-op.
• Folded into unreleased 3.5.1; CHANGELOG names the consumers.

Consumers switch after the train publishes 3.5.1.

🤖 Generated with Claude Code