unifying pixi run and pixi task list

[Incharajayaram]

Description

This PR unifies the output format of pixi run (when called without arguments) and pixi task list commands to provide a consistent user experience.

Before:
When running pixi run without arguments, users would see a simple list:

Available tasks:
        build-linux
        build-osx
        cran

After:
Now pixi run shows the same detailed output as pixi task list:

Tasks that can run on this machine:
-----------------------------------
build-linux, build-osx, cran, cran-v0, lint, pypi, pypi-v0

Task         Description
build-linux  build for Linux inside a docker container
build-osx    build directly on a MacOS host machine
cran         generate a v1 (rattler-build) recipe for a CRAN package name with `grayskull`

Changes Made:

• Modified the command_not_found() function in crates/pixi_cli/src/run.rs to use the print_tasks() function, which provides detailed task information including descriptions
• This function is called both when pixi run is executed without arguments and when a task is not found (exit code 127)

Fixes #5276

How Has This Been Tested?

Tested by running the following commands in a workspace with defined tasks:

# Build the project
cargo build -p pixi

# Test unified output
./target/release/pixi run

# Compare with task list (should now match)
./target/release/pixi task list

Both commands now display the same formatted output with task names and descriptions.

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
  • I take responsibility for any AI-generated content in my PR.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added sufficient tests to cover my changes.
• I have verified that changes that would impact the JSON schema have been made in schema/model.py.

[baszalmstra]

This was already implemented in #5318, although not yet merged, this implementation was there first, so I'll first check if we can merge that.