Add SDK persistence and configurable edge location

- Add external SDK installation (wp-content/twilio-sdk/) that survives
  WordPress plugin updates
- Add install-twilio-sdk-external.sh script for external SDK setup
- Update SDK loading to check external location first, internal fallback
- Add post-update detection hook to warn if SDK was deleted
- Add configurable Twilio Edge Location setting (default: roaming)
- Fix US calls failing due to hardcoded Sydney edge location

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -6,6 +6,7 @@
 - **URL**: `https://phone.cloud-hosting.io/`
 - **Deployment**: rsync to Docker (remote server only, not local)
 - **SDK**: Twilio PHP SDK v8.7.0
+- **External SDK**: `wp-content/twilio-sdk/` (survives plugin updates)
 
 ## Phone Variable Names
 **Use**: `incoming_number`, `agent_number`, `customer_number`, `workflow_number`, `queue_number`, `default_number`  
@@ -47,6 +48,25 @@ $api->update_call($customer_call_sid, ['twiml' => $twiml_xml]);
 - Firefox support added
 - 1-min agent status auto-revert
 
+## SDK Installation
+- **External SDK (Recommended)**: Use `install-twilio-sdk-external.sh` to install SDK to `wp-content/twilio-sdk/`
+  - Survives WordPress plugin updates
+  - SDK location defined by `TWP_EXTERNAL_SDK_DIR` constant
+  - Loading priority: External first, then internal `vendor/` fallback
+- **Internal SDK (Alternative)**: Use `install-twilio-sdk.sh` to install to `vendor/`
+  - Will be deleted when WordPress updates the plugin
+  - Requires reinstallation after each plugin update
+- **SDK Loading**: Plugin checks external location first via autoloader, falls back to internal
+- **Post-Update Detection**: Hook on `upgrader_process_complete` checks SDK status and shows warning
+
+## Browser Phone Configuration
+- **Edge Location Setting**: Configurable via Settings → Twilio Edge Location
+  - Default: `roaming` (auto-select closest edge)
+  - Options: ashburn, umatilla, dublin, frankfurt, singapore, sydney, tokyo, sao-paulo
+  - Stored in: `twp_twilio_edge` option
+  - Used by: Browser phone JavaScript for WebRTC connection
+  - Critical: Wrong edge causes immediate call failures (e.g., US calls with Sydney edge)
+
 ## Development Notes
 - **API**: E.164 format (+1XXXXXXXXXX)
 - **Database**: Use `$wpdb`, prepared statements
@@ -61,5 +81,28 @@ $api->update_call($customer_call_sid, ['twiml' => $twiml_xml]);
 - ElevenLabs TTS with Alice fallback
 - 68 AJAX actions, 26 REST endpoints
 
+## Recent Technical Changes (v2.8.9)
+
+### SDK Persistence Between Plugin Updates
+- **Problem**: WordPress plugin updates delete entire plugin folder including `vendor/` SDK
+- **Solution**: External SDK installation at `wp-content/twilio-sdk/` survives updates
+- **Implementation**:
+  - New constant: `TWP_EXTERNAL_SDK_DIR` points to `wp-content/twilio-sdk/`
+  - Loading priority in `twp_check_sdk_installation()`: External first, internal fallback
+  - Classes updated: `TWP_Twilio_API`, `TWP_Webhooks` constructors check external location first
+  - New script: `install-twilio-sdk-external.sh` automates external installation
+  - Post-update hook: `twp_check_sdk_after_update()` detects missing SDK after updates
+  - Admin notices: `twp_sdk_missing_notice()` shows both installation options
+  - Warning system: `twp_show_sdk_update_warning()` via transient after plugin updates
+
+### US Calls Failing Fix (Browser Phone)
+- **Problem**: Browser phone had hardcoded `edge: 'sydney'`, causing US calls to fail with immediate HANGUP
+- **Solution**: Configurable edge location via WordPress settings
+- **Implementation**:
+  - New setting: `twp_twilio_edge` with default value `roaming`
+  - Settings UI: Dropdown in admin settings with 8 edge options
+  - Browser phone JS: Uses `get_option('twp_twilio_edge', 'roaming')` instead of hardcoded value
+  - Edge options: roaming, ashburn, umatilla, dublin, frankfurt, singapore, sydney, tokyo, sao-paulo
+
 ---
-*Updated: Sept 2025*
+*Updated: Jan 2026*