chore: add PHPDoc descriptions to types and request classes

Enrich dozens of PHP type and request classes with class-level PHPDoc
summaries and inline property descriptions. No public API signatures,
method names, or behavioral logic were changed — only documentation
comments were added or expanded.

Key changes:
- Add class-level PHPDoc blocks to types such as `Assistant`, `Call`, `Edge`, `CompliancePlan`, `BackoffPlan`, and many more
- Expand inline `@var` descriptions for properties like `firstMessageInterruptionsEnabled`, `compliancePlan`, `keypadInputPlan`, `baseDelaySeconds`, and `excludedStatusCodes`
- Improve property descriptions across insight DTOs (`BarInsight`, `LineInsight`, `PieInsight`, `TextInsight`) and credential DTOs (`CreateTwilioCredentialDto`, `CreateVonageCredentialDto`, etc.)

🌿 Generated with Fern

Author: fern-api[bot]

changelog.md

@@ -1,3 +1,5 @@
+## [2.0.1] - 2026-07-20
+
 ## 2.0.0 - 2026-06-24
 ### Breaking Changes
 * **`CartesiaExperimentalControlsSpeedZero`** has been renamed to `CartesiaSpeedControlZero`. Update any references to this enum in your code to use the new name.