fix(a11y): correct select chevron role and type rangepicker aria-label props

[nroshan-eightfold]

SUMMARY:

Two WCAG-related accessibility fixes surfaced by the Eightfold condition / If-Then builder.

1. Select chevron (WCAG 4.1.2): the dropdown toggle chevron rendered as role="presentation" + aria-hidden="true" with an aria-label. A presentational role on a <button> strips its semantics and the aria-label is ignored — an inconsistent state axe flags as a presentation-role conflict. Since the role="combobox" input already owns open/close (aria-expanded / aria-controls), this removes role="presentation" and keeps aria-hidden, so the chevron is cleanly hidden from assistive tech per the combobox pattern.
2. RangePicker date-input aria labels (typing / DX): startDateInputAriaLabel / endDateInputAriaLabel are consumed by the internal range picker but were declared only on a local type, so they were missing from the public .d.ts. Consumers had to cast (as unknown as …) to name the start/end date inputs. They're now on the public OcRangePickerSharedProps, so the cast can be dropped downstream.

GITHUB ISSUE (Open Source Contributors)

N/A

JIRA TASK (Eightfold Employees Only):

https://eightfoldai.atlassian.net/browse/ENG-203981

CHANGE TYPE:

• Bugfix Pull Request
• Feature Pull Request

TEST COVERAGE:

• Tests for this change already exist
• I have added unittests for this change

TEST PLAN:

Issue 1 — Select chevron (WCAG 4.1.2)

Verified in Storybook (Select → Basic) by inspecting the chevron <button> on main vs this branch:

• Before (main / 2.58.4): <button aria-hidden="true" role="presentation" tabindex="-1" aria-label="Toggle dropdown"> — presentational role on an interactive button with an ignored label. axe flags it as 1 Incomplete ("ARIA role presentation must be removed when the element is made visible, as it is not allowed for the element").
• After (this PR): <button aria-hidden="true" tabindex="-1" aria-label="Toggle dropdown"> — role="presentation" removed, aria-hidden retained. axe: 0 violations / 0 incomplete. The role="combobox" input remains the interaction surface.
• Keyboard: Tab skips the chevron; the combobox input opens/closes via Enter / ↓ / Esc.
• VoiceOver: announces only the combobox — no separate "Toggle dropdown" button.

Before:

After:

Issue 3a — RangePicker aria-label prop types

Verified via the type system + compiled output (this is a type change, not a runtime one):

• yarn typecheck → clean. The props type-check across the codebase; on main they were not usable without a cast.

• The props are now emitted in the public .d.ts:

  lib/components/DateTimePicker/Internal/OcPicker.types.d.ts
    932:  startDateInputAriaLabel?: string;
    934:  endDateInputAriaLabel?: string;
  

  → <RangePicker startDateInputAriaLabel="…" endDateInputAriaLabel="…" /> now type-checks with no as unknown as … cast downstream.

Regression

• Full unit suite green in pre-commit: 222 suites / 2645 tests pass.
• Select snapshots regenerated — the only rendered-DOM change is the removed role="presentation" on the chevron; no behavioral change (mouse onClick and keyboard combobox interaction unchanged).

Note: this PR covers Issue 1 and Issue 3a from ENG-203981. Issues 2 (keyboard-active option contrast) and 3b (RangePicker aria passthrough) were already satisfied in octuple 2.58.4 and need no change here.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.00%. Comparing base (daa8ea0) to head (f62a472).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1156      +/-   ##
==========================================
- Coverage   85.00%   85.00%   -0.01%     
==========================================
  Files        1230     1230              
  Lines       21588    21587       -1     
  Branches     8209     8209              
==========================================
- Hits        18351    18350       -1     
  Misses       3151     3151              
  Partials       86       86              

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[agupta-eightfold]

lgtm

[bgharu-eightfold]

LGTM