fix(calm-suite): tighten CalmArchitecture + downstream guards for calm-models adoption

Resolves the remaining tsc errors after pulling in @finos/calm-models:

  1. CalmCoreSchema makes `nodes?` and `relationships?` optional. With
     exactOptionalPropertyTypes:true, every direct `arch.nodes`
     access errors. Studio's producers always populate both arrays
     (empty if blank), so the studio-side CalmArchitecture alias
     tightens both fields to required via
     `Omit<CalmCoreSchema, 'nodes' | 'relationships'> & { ... }`.
     Removes the flood of TS18048 errors across mcp-server,
     apps/studio, and validation.ts.

  2. mcp-server/src/tools/render.ts: the variant-branch closures
     lose narrowing inside forEach because calm-models' nested
     `relationship-type` uses all-optional keys (not exclusive
     discriminated union). Bind narrowed branch to a local const
     before entering the closure.

  3. mcp-server tests/aigf-helpers.test.ts: 9 node literals missing
     the now-required `description` field — bulk add via the
     unique-id label as the description string.

Workspace dep spec changed from "*" to "file:../../../../calm-models"
because calm-suite/calm-studio is a sub-monorepo with its own
workspaces array; npm in the sub-tree cannot resolve a "*" spec to
the parent workspace. The file: path works in both the parent root
workspace install and the sub-monorepo install.

Test results: 419 + 78 + 51 + 80 + 10 + 21 + 17 = 676 passing + 1 todo
across all 7 calm-suite/calm-studio workspaces.

Signed-off-by: Gourav Shah <gjs@opsflow.sh>

Author: gjs-opsflo