Standardize formatting in backfill changelog entry

Use consistent numbered lists with **Title**: Description pattern
throughout all sections. Remove mixed bullet/numbered lists and
inline code formatting that caused font inconsistencies.

https://claude.ai/code/session_01PKuW5yr6fMdr6mSwX5Gchy

Author: claude

fern/changelog/2026-03-31.mdx

@@ -28,43 +28,52 @@ Here's a summary of everything we shipped from October 2025 through March 2026.
 
 ### Transcriber Models (Speech-to-Text)
 
-- **Deepgram Nova-3 Languages** — Added Hebrew, Urdu, Tagalog, and Arabic bilingual support
-- **Cartesia Transcriber** — ink-whisper
-- **Soniox** — stt-rt-v4
+1. **Deepgram Nova-3 Languages**: Added Hebrew, Urdu, Tagalog, and Arabic bilingual support.
+
+2. **Cartesia Transcriber**: ink-whisper.
+
+3. **Soniox**: stt-rt-v4.
 
 ### Intelligence Models (LLM)
 
-- **GPT-5 Family** — OpenAI's latest intelligence models, including GPT-5, 5-Mini, 5-Nano, 5.1, 5.2, 5.4, 5.4-Mini, 5.4-Nano
-- **Claude 4.5–4.6** — Anthropic's latest intelligence models Sonnet 4.5, Opus 4.5, Opus 4.6, Sonnet 4.6
-- **Gemini 3 Flash** — Google's latest intelligence models
-- **Grok 4 Fast** — Reasoning and non-reasoning variants
-- **GPT Realtime Mini**
+1. **GPT-5 Family**: OpenAI's latest intelligence models, including GPT-5, 5-Mini, 5-Nano, 5.1, 5.2, 5.4, 5.4-Mini, 5.4-Nano.
+
+2. **Claude 4.5–4.6**: Anthropic's latest intelligence models Sonnet 4.5, Opus 4.5, Opus 4.6, Sonnet 4.6.
+
+3. **Gemini 3 Flash**: Google's latest intelligence models.
+
+4. **Grok 4 Fast**: Reasoning and non-reasoning variants.
+
+5. **GPT Realtime Mini**: OpenAI's lightweight realtime model.
 
 ### Voice Models (Text-to-Speech)
 
-- **Cartesia** — sonic-3, sonic-3-2026-01-12, sonic-3-2025-10-27
-- **WellSaid** — Caruso (new), legacy
-- **Inworld** — inworld-tts-1 (REST, original), inworld-tts-1.5-max (WebSocket, $10/M chars), inworld-tts-1.5-mini (WebSocket, $5/M chars)
-- **ElevenLabs Scribe v2**
+1. **Cartesia**: sonic-3, sonic-3-2026-01-12, sonic-3-2025-10-27.
+
+2. **WellSaid**: Caruso (new), legacy.
+
+3. **Inworld**: inworld-tts-1 (REST, original), inworld-tts-1.5-max (WebSocket, $10/M chars), inworld-tts-1.5-mini (WebSocket, $5/M chars).
+
+4. **ElevenLabs Scribe v2**: Latest version of ElevenLabs speech-to-text.
 
 ---
 
 ## Developer Tools & API
 
 1. **Structured Outputs Improvements**: Updates to our AI-powered analysis and data extraction tool, including transient structured outputs, audio-based extraction, and regex extraction.
 
-2. **SIP Request Tool + DTMF over SIP INFO**
+2. **SIP Request Tool + DTMF over SIP INFO**: Send SIP requests and DTMF tones via SIP INFO messages during calls.
 
-3. **Variable Passing Between Tool Calls**
+3. **Variable Passing Between Tool Calls**: Pass output variables from one tool call as input to subsequent tool calls.
 
-4. **Encrypted Tool Arguments**
+4. **Encrypted Tool Arguments**: Encrypt sensitive tool arguments to protect data in transit.
 
-5. **Low Confidence Speech Hook**
+5. **Low Confidence Speech Hook**: Hook that triggers when the transcriber returns low-confidence speech results.
 
-6. **Time Elapsed Hook**
+6. **Time Elapsed Hook**: Hook that triggers at specified time intervals during a call.
 
-7. **`assistant.speechStarted` Event**
+7. **assistant.speechStarted Event**: New event fired when the assistant begins speaking.
 
-8. **MCP Improvements** — Bearer auth, `$ref` dereferencing, child tool messages/discovery
+8. **MCP Improvements**: Bearer auth, $ref dereferencing, child tool messages/discovery.
 
-9. **Warm Transfer Improvements** — SIP support, caller ID, context engineering, variable filling
+9. **Warm Transfer Improvements**: SIP support, caller ID, context engineering, variable filling.