fix: wire allowed_tools/disallowed_tools inputs through to Claude SDK

The disallowed tools env var read in run.ts was DISALLOWED_TOOLS_INPUT
(raw user input) instead of DISALLOWED_TOOLS (computed value including
WebSearch/WebFetch defaults). This meant default tool disallowance was
never enforced. Also removes orphaned ALLOWED_TOOLS env var export from
createPrompt() (tag mode passes allowed tools via claudeArgs instead),
extracts shared parseToolsInput utility to eliminate duplication, and
adds tests.

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

docs/forgejo.md

@@ -159,6 +159,37 @@ platform:
 
 All other inputs work identically on both platforms. See the [Usage Guide](./usage.md) for the full list.
 
+## Fork-Specific Fixes (All Platforms)
+
+This fork fixes upstream bugs that affect **both GitHub and Forgejo** usage:
+
+### `allowed_tools` / `disallowed_tools` inputs now work (upstream #181, #287, #724)
+
+Upstream's `allowed_tools` and `disallowed_tools` inputs are completely broken — they are never wired through to Claude execution. This affects tag mode (the `@claude` mention flow) where the tool list is hardcoded and user inputs are silently ignored.
+
+**What was broken:**
+
+- `allowed_tools` was not defined in `action.yml`, so the env var was never set
+- Tag mode only merged `mcp__github_*` tools from `claude_args`, filtering out everything else
+- `run.ts` never passed `allowedTools`/`disallowedTools` to `runClaude()`
+- `createPrompt()` hardcoded `WebSearch` and `WebFetch` as disallowed with no way to override
+
+**What this fork fixes:**
+
+- Added `allowed_tools` and `disallowed_tools` as proper action inputs
+- User tools are merged into the tag-mode tool list
+- `disallowedTools` is passed through to the SDK
+- `WebSearch`/`WebFetch` are removed from the disallowed list when included in `allowed_tools`
+
+**Usage:**
+
+```yaml
+- uses: actions/claude-code-action@main
+  with:
+    allowed_tools: "WebSearch,WebFetch"
+    # All other inputs as usual
+```
+
 ## Dedicated Bot User (Recommended)
 
 On GitHub, Claude gets its own identity via the GitHub App (`claude[bot]`). On Forgejo, there's no such mechanism — by default the action runs under whatever token you provide, meaning commits and comments appear as the human user.