feat: auto-detect project name from manifest files

- Add --name flag to override auto-detected project name
- Add RenameNode method to DAG for renaming __project__ root
- Extract project name from manifests:
  - Cargo.toml: [package].name
  - go.mod: module directive
  - package.json: name field
  - composer.json: name field
  - pom.xml: groupId:artifactId
  - poetry.lock/requirements.txt: pyproject.toml (sibling)
  - Gemfile: *.gemspec (sibling)
- Add example pyproject.toml and gemspec files

Author: matzehuels

README.md

@@ -78,6 +78,22 @@ stacktower parse go examples/manifest/go.mod -o deps.json
 
 When the argument exists on disk or matches a known manifest filename, Stacktower automatically parses it as a manifest.
 
+The project name (root node) is auto-detected from the manifest or a sibling file:
+- **Cargo.toml**: `[package].name`
+- **go.mod**: `module` directive
+- **package.json**: `name` field
+- **composer.json**: `name` field
+- **pom.xml**: `groupId:artifactId`
+- **poetry.lock / requirements.txt**: `pyproject.toml` (sibling)
+- **Gemfile**: `*.gemspec` (sibling)
+
+Use `--name` to override the auto-detected name:
+
+```bash
+stacktower parse python requirements.txt --name="my-project" -o deps.json
+stacktower parse ruby Gemfile -n my-rails-app -o deps.json
+```
+
 #### Explicit Mode
 
 Force registry or manifest parsing when auto-detection isn't enough:
@@ -165,6 +181,7 @@ stacktower render examples/test/diamond.json -o diamond.svg
 | Flag | Description |
 |------|-------------|
 | `-o`, `--output` | Output file (stdout if empty) |
+| `-n`, `--name` | Project name for manifest parsing (auto-detected from manifest if not set) |
 | `--max-depth N` | Maximum dependency depth (default: 10) |
 | `--max-nodes N` | Maximum packages to fetch (default: 5000) |
 | `--enrich` | Enrich with GitHub metadata (default: true, requires `GITHUB_TOKEN`) |

examples/manifest/example-app.gemspec

@@ -0,0 +1,13 @@
+Gem::Specification.new do |spec|
+  spec.name = "example-ruby-app"
+  spec.version = "1.0.0"
+  spec.authors = ["Example Author"]
+  spec.summary = "Example Ruby application for testing stacktower"
+
+  spec.files = Dir["lib/**/*"]
+  spec.require_paths = ["lib"]
+
+  spec.add_dependency "rails", "~> 7.1"
+  spec.add_dependency "pg", "~> 1.1"
+end
+

examples/manifest/pyproject.toml

@@ -0,0 +1,26 @@
+[project]
+name = "example-python-project"
+version = "0.1.0"
+description = "Example project for testing stacktower manifest parsing"
+requires-python = ">=3.9"
+dependencies = [
+    "requests>=2.28.0",
+    "click>=8.0.0",
+    "pydantic>=2.0.0",
+    "httpx>=0.24.0",
+    "rich>=13.0.0",
+]
+
+[tool.poetry]
+name = "example-python-project"
+version = "0.1.0"
+description = "Example project for testing stacktower manifest parsing"
+
+[tool.poetry.dependencies]
+python = "^3.9"
+requests = "^2.28.0"
+click = "^8.0.0"
+pydantic = "^2.0.0"
+httpx = "^0.24.0"
+rich = "^13.0.0"
+