fix(studio): use slotStart instead of removed slotLeft on row-action menu items

[aray12]

Summary

@nvidia/foundations-react-core's Dropdown renamed its menu-item icon slot from slotLeft/slotRight to slotStart/slotEnd; every rowActionsColumn call site in Studio still used the old slotLeft key, so row-action icons were silently dropped (the KUI Dropdown only reads item.slotStart). This PR renames all affected call sites and adds explicit DropdownEntry[] return types to every rowActions callback so TypeScript's excess-property check catches this class of typo going forward — it didn't catch it here because the callbacks were untyped inline arrow functions returned from a callback-argument position, which TypeScript does not excess-property-check.

Related Issue

None.

Changes

• Renamed slotLeft → slotStart on row-action menu items in: FileRowEditor/columns.tsx, SecretsDataView, DeploymentsDataView, MembersDataView, GuardrailsDataView, and the shared StudioDataView.stories.tsx (3 story blocks).
• Added explicit DropdownEntry[] return-type annotations to the rowActions callback on all of the above, plus six more rowActionsColumn call sites that were already correct but shared the same untyped-callback blind spot: InferenceProvidersDataView, VirtualModelsDataView, AgentsDataView, DatasetsTable, OptimizerRoute, CustomModelsDataView.
• No behavior change other than the row-action icons now rendering; the hardening-only files have identical menu items/behavior, just compiler-checked now.

Type of Change

• Code change (feature, bug fix, or refactor)
• Code change with documentation updates
• Documentation only
• Contributor tooling or automation
• CI, build, or test infrastructure

Quality Gates

• Tests added or updated for changed behavior
• Existing tests cover changed behavior — justification: pure prop rename + type annotation, no new logic; existing component/data-view tests continue to exercise these rowActionsColumn call sites and would fail on a real regression to the menu structure.
• Tests not applicable — justification:
• Documentation updated for user-visible behavior
• Documentation not applicable — justification: no user-facing docs describe this internal Dropdown prop.

Verification

• Pull request title follows the repository's Conventional Commit format
• Every commit includes an appropriate Signed-off-by: trailer
• uv run pre-commit run -a passes, or any blocked checks are identified below
• Targeted tests pass, or tests are marked not applicable above
• No secrets, API keys, or credentials are included

Targeted validation:

• pnpm --filter nemo-studio-ui typecheck — passed
• pnpm --filter @nemo/common typecheck — passed
• pnpm --filter="...[origin/main]" run --parallel --if-present typecheck (PR-scoped, mirrors CI) — passed
• pnpm lint:fix (web/) — passed, no warnings
• uv run pre-commit run -a — passed, with two pre-existing environment-only failures unrelated to this change (not caused by any file in this PR): helm-docs hook fails because the helm-docs binary isn't installed in this sandbox; uv-lock hook fails because the sandbox's local uv (0.9.28) differs from the pinned platform uv (0.9.14). Neither hook touched a file in this diff (0 Helm/Python/uv.lock files changed).
• pnpm --filter="...[origin/main]" run --parallel --if-present test:ci (PR-scoped, packages/common + packages/studio) — passed, exit code 0, no failing tests.
• Manual sanity check: temporarily reintroduced a typo'd extra prop on one fixed call site (SecretsDataView) and confirmed tsc now reports TS2353: Object literal may only specify known properties, then reverted — confirms the excess-property check is genuinely restored, not just cosmetically annotated.
• Manual browser verification (opening each affected data view/Storybook story to visually confirm icons render) was not performed in this session — flagging as still worth a look before merge.

[github-actions]

Suite	Lines Covered	Line Rate	Branch Rate
Unit Tests	33340/42105	79.2%	64.1%
Integration Tests	N/A	N/A	N/A