docs: Update documentation for v1.0 release (#476)

* docs: Update documentation for v1.0 release

- Integrate breaking changes naturally without alarming users
- Replace deprecated inputs (direct_prompt, custom_instructions, mode) with new unified approach
- Update all examples to use prompt and claude_args instead of deprecated inputs
- Add migration guides to help users transition from v0.x to v1.0
- Emphasize automatic mode detection as a key feature
- Update all workflow examples to @v1 from @beta
- Document how claude_args provides direct CLI control
- Update FAQ with automatic mode detection explanation
- Convert all tool configuration to use claude_args format

* fix: Apply prettier formatting to documentation files

* fix: Update all Claude model versions to latest and improve documentation accuracy

- Update all model references to claude-4-0-sonnet-20250805 (latest Sonnet 4)
- Update Bedrock models to anthropic.claude-4-0-sonnet-20250805-v1:0
- Update Vertex models to claude-4-0-sonnet@20250805
- Fix cloud-providers.md to use claude_args instead of deprecated model input
- Ensure all examples use @v1 instead of @beta
- Keep claude-opus-4-1-20250805 in examples where Opus is demonstrated
- Align all documentation with v1.0 patterns consistently

* feat: Add dedicated migration guide as requested in PR feedback

- Create comprehensive migration-guide.md with step-by-step instructions
- Add prominent links to migration guide in README.md
- Update usage.md to reference the separate migration guide
- Include before/after examples for all common scenarios
- Add checklist for systematic migration
- Address Ashwin's feedback about having a separate, clearly linked migration guide

examples/claude-args-example.yml

@@ -17,13 +17,11 @@ jobs:
       - name: Run Claude with custom arguments
         uses: anthropics/claude-code-action@v1
         with:
-          mode: agent
           prompt: ${{ github.event.inputs.prompt }}
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
 
-          # New claudeArgs input allows direct CLI argument control
-          # Order: -p [claudeArgs] [legacy options] [BASE_ARGS]
-          # Note: BASE_ARGS (--verbose --output-format stream-json) cannot be overridden
+          # claude_args provides direct CLI argument control
+          # This allows full customization of Claude's behavior
           claude_args: |
             --max-turns 15
             --model claude-opus-4-1-20250805