docs: Add uv installation guide and inline callouts

[Copilot]

Users hitting command not found: uv or command not found: uvx had no in-repo guidance on installing uv, despite it being the primary install path for Spec Kit.

Changes

• docs/install/uv.md — new dedicated uv installation page covering all platforms (standalone curl/irm installers, Homebrew, WinGet, Scoop), a verification step, and a link to official Astral docs
• README.md — [!NOTE] callout added before the first uv tool install block in the "Option 1: Persistent Installation" section pointing users to the new guide
• docs/installation.md — [!NOTE] callout added before the first uvx block in "Initialize a New Project" with the same pointer
• docs/toc.yml — registers install/uv.md under the Getting Started section

[Copilot]

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 2

[mnriem]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Done in 7c19385:

• Line 18: Replaced the shell-specific source $HOME/.local/bin/env hint with "follow any instructions printed by the installer to add uv to your PATH, then open a new terminal" — works regardless of shell.
• Lines 22–26: Changed "run the following in PowerShell" to "Run the following in Command Prompt or PowerShell" — makes it clear the command (which spawns a powershell subprocess) can be executed from either environment.

[Copilot]

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 1

[mnriem]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Done in 3cca2f5. Updated the note to read: "The uv tool install commands below require uv … The pipx alternative does not require uv." — makes it clear the uv requirement is scoped only to the uv tool install lines, not the pipx option.

[Copilot]

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 1

[mnriem]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Done in 1922ff9. The note in docs/installation.md now reads: "The uvx commands below require uv … The pipx alternative does not require uv." — matching the same pattern applied to the README note.

[Copilot]

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 0 new