Abort execution when installation fails

[bradhe]

Title says it all. When uv venv or uv sync fails during app startup, execution now aborts immediately with a Crashed status (because the developer needs to fix the issue) instead of continuing. Added 05-broken-dependencies example app with an intentionally non-existent package and added test_abort_on_dependency_installation_failure test that verifies the app crashes with a non-zero exit code when dependency installation fails.

This was probably historically missed because the apps would fail anyway along the way.

[Copilot]

Pull request overview

This PR ensures that application execution aborts immediately when dependency installation fails during startup, rather than continuing with broken dependencies. The implementation adds proper error handling for uv venv and uv sync failures, returning Crashed status with appropriate error variants.

Changes:

• Added error handling to abort execution when uv venv or uv sync processes exit with non-zero codes
• Created a test example app with intentionally broken dependencies to verify failure behavior
• Added test case to verify apps crash with non-zero exit code when dependency installation fails

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/tower-runtime/src/local.rs	Added exit code checks for venv creation and dependency sync processes, returning errors when they fail
crates/tower-runtime/src/errors.rs	Added DependencyInstallationFailed error variant
crates/tower-runtime/tests/local_test.rs	Added test to verify crash behavior on dependency installation failure
crates/tower-runtime/tests/example-apps/05-broken-dependencies/pyproject.toml	Created test app with non-existent dependency
crates/tower-runtime/tests/example-apps/05-broken-dependencies/main.py	Added placeholder script that should never execute
crates/tower-runtime/tests/example-apps/05-broken-dependencies/Towerfile	Created Towerfile configuration for broken dependencies test app

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