refactor: complete v1.0 simplification by removing all legacy inputs

- Remove all backward compatibility for v1.0 simplification
- Remove 10 legacy inputs from base-action/action.yml
- Remove 9 legacy inputs from main action.yml
- Simplify ClaudeOptions type to just timeoutMinutes and claudeArgs
- Remove all legacy option handling from prepareRunConfig
- Update tests to remove references to deleted fields
- Remove obsolete test file github/context.test.ts
- Clean up types to remove customInstructions, allowedTools, disallowedTools

Users now use claudeArgs exclusively for CLI control.

examples/claude-args-example.yml

@@ -0,0 +1,32 @@
+name: Claude Args Example
+
+on:
+  workflow_dispatch:
+    inputs:
+      prompt:
+        description: "Prompt for Claude"
+        required: true
+        type: string
+
+jobs:
+  claude-with-custom-args:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - 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: |
+            --max-turns 15
+            --model claude-3-opus-20240229
+            --allowedTools Edit,Read,Write,Bash
+            --disallowedTools WebSearch
+            --system-prompt "You are a senior engineer focused on code quality"