[BUG]: formatDate breaks quoted literals and EEE since date-fns was removed #2937

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Describe the Bug

formatDate is specified as taking a Unicode TR35 date pattern. Since web_core 0.12.0 dropped date-fns, the token regex in typescript/web_core/src/common/basic_functions.ts:294 does not know TR35 quoted literals and has no EE/EEE tokens:

• "MMM d 'at' h:mm a" renders Feb 2 'PMt' 3:17 PM: the a inside 'at' is read as the AM/PM token and the quotes are kept.
• "EEE, MMM d" renders MonMonMon, Feb 2: EEE is matched as three E tokens.

Two of the v0.9.1 basic catalog examples use a quoted literal and render wrong in the published @a2ui/react 0.12.0:

• specification/v0_9_1/catalogs/basic/examples/16_workout-summary.json:136 ("EEEE, MMM d 'at' h:mm a") shows Monday, Dec 15 'AMt' 7:30 AM
• specification/v0_9_1/catalogs/basic/examples/30_live-invitation-builder.json:169 ("EEEE, MMMM d, yyyy 'at' h:mm a") shows Tuesday, July 15, 2025 'PMt' 7:00 PM

@a2ui/web_core 0.11.0 (date-fns) renders both correctly. The Python a2ui_core uses the same regex (basic_catalog/v0_9/function_impls.py and v1_0/function_impls.py), so it has the same output. Swift uses DateFormatter and is fine.

Steps to Reproduce

import {FormatDateImplementation} from '@a2ui/web_core/v0_9/basic_catalog';

const value = '2026-02-02T15:17:09Z';
for (const format of ["MMM d 'at' h:mm a", 'EEE, MMM d', "h 'o''clock'"]) {
  console.log(FormatDateImplementation.execute({value, format}));
}

Expected Behavior

Feb 2 at 3:17 PM
Mon, Feb 2
3 o'clock

Actual:

Feb 2 'PMt' 3:17 PM
MonMonMon, Feb 2
3 'o''clock'

Environment Details

• OS: Ubuntu
• Browser/Platform: Node.js 22; Python 3.13
• SDK/Package Name & Version: @a2ui/web_core 0.12.0, @a2ui/react 0.12.0, a2ui-core (main at 102ec1a)
• Protocol Version: v0.9.1
• Agent Framework & LLM Model: n/a

Additional Context

Happy to send a PR for both engines: match a quoted literal as one token and emit its text, map '' to an apostrophe, and give EE/EEE the abbreviated weekday. The shared conformance/core/functions.yaml has one formatDate case; quoted-literal cases could go there too once the other SDKs are checked against it.