Add a visible per-part bend-table manager

[protosphinx]

Why this matters

Bend tables already drive associative K-factor resolution, but users can author them only through typed operations.

Scope

• Add a manager for 1 to 64 { thickness, bendRadius, kFactor } rows.
• Route changes through sheetMetal.bendTable.set and deletion through sheetMetal.bendTable.delete.
• Display the canonical sorted order after apply.
• When a table is active, make flange dialogs explain that K-factor comes from the exact matching row.
• Do not add gauge tables, interpolation, unit conversion, or CSV import.

Relevant files

• src/page.html
• src/static/studio.js
• src/static/studio-v6-ui-registry.js
• scripts/studio-sheet-metal-smoke.ts
• docs/sheet-metal.md

Acceptance evidence

• Unsorted visible input persists in canonical thickness and radius order.
• Editing a row associatively updates every dependent flange K-factor and bend allowance.
• Exact folded bodies rebuild successfully after the update.
• Missing row, duplicate row, and invalid value failures do not mutate the project.
• Deleting the table freezes current resolved values as documented.
• Save and reopen preserve the same canonical table and exact body evidence.

Test commands

npm run build
npm run smoke:sheet-metal
npm run smoke:ui-foundation
npm run smoke:browser
npm run ci:gate

Contribution size

M: a small table editor over an existing typed lifecycle, with associative rebuild coverage.

Maintainer response expectation

Post the short UI or fixture approach requested above and wait for maintainer scope confirmation before implementation. Review will focus on the listed acceptance evidence.