feat(skills): add image vision skill for WhatsApp (#770)

* chore: prepare image-vision skill for template regeneration

- Delete stale modify/*.ts templates (built against 1.1.2)
- Update core_version to 1.2.6
- Strip fork-specific details from intent docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat(skills): regenerate image-vision modify/ templates against upstream

Templates regenerated against upstream 1.2.6:
- src/container-runner.ts: imageAttachments field in ContainerInput
- src/index.ts: parseImageReferences + threading to runAgent
- src/channels/whatsapp.ts: downloadMediaMessage + image handling block
- src/channels/whatsapp.test.ts: image mocks + 4 test cases
- container/agent-runner/src/index.ts: ContentBlock types, pushMultimodal, image loading

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: update image-vision tests for upstream templates

- Relax downloadMediaMessage import pattern check (multi-line import)
- Remove check for [Image - processing failed] (not in upstream template)
- Add vitest.skills.config.ts for skill package test runs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: update image-vision core_version to 1.2.8

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/add-image-vision/modify/container/agent-runner/src/index.ts.intent.md

@@ -0,0 +1,23 @@
+# Intent: container/agent-runner/src/index.ts
+
+## What Changed
+- Added `imageAttachments?` field to ContainerInput interface
+- Added `ImageContentBlock`, `TextContentBlock`, `ContentBlock` type definitions
+- Changed `SDKUserMessage.message.content` type from `string` to `string | ContentBlock[]`
+- Added `pushMultimodal(content: ContentBlock[])` method to MessageStream class
+- In `runQuery`: image loading logic reads attachments from disk, base64-encodes, sends as multimodal content blocks
+
+## Key Sections
+- **Types** (top of file): New content block interfaces, updated SDKUserMessage
+- **MessageStream class**: New pushMultimodal method
+- **runQuery function**: Image loading block
+
+## Invariants (must-keep)
+- All IPC protocol logic (input polling, close sentinel, message stream)
+- MessageStream push/end/asyncIterator (text messages still work)
+- readStdin, writeOutput, log functions
+- Session management (getSessionSummary, sessions index)
+- PreCompact hook (transcript archiving)
+- Bash sanitization hook
+- SDK query options structure (mcpServers, hooks, permissions)
+- Query loop in main() (query -> wait for IPC -> repeat)