feat(fish-deps): add uv as managed dep; install before cargo and fish

uv is now listed first in the catalog (before cargo and fish) so it is
installed automatically before the fish source build is attempted.
Install uses the official curl script; update uses `uv self update`.

Catalog order is now: uv → cargo → fish → … ensuring prerequisites are
in place before any dependent install method runs.

README updated: uv and cargo added to the Required table, warning callout
and dependency management note reflect the automatic install flow.

README.md

@@ -257,7 +257,7 @@ rm -f file.txt  # Falls through to standard rm -f
 Install method priority: **git+cargo source build** (fish) → **cargo** (other Rust tools, gets latest crate) → **system PM** (paru/apt/brew/etc.) → **git clone** (fzf) → **curl installer** (starship, fisher) → **pipx** (Python tools). When multiple methods are available for a tool, you are prompted to choose.
 
 > [!NOTE]
-> Upgrading Fish from source requires **cargo** and **[uv](https://docs.astral.sh/uv/)**. If either is missing, `fish-deps install`/`update` will fall back to the system package manager instead.
+> Upgrading Fish from source requires **cargo** and **[uv](https://docs.astral.sh/uv/)**. Both are managed dependencies — `fish-deps install` will offer to install them before attempting the Fish build. If both are unavailable, `fish-deps update` falls back to the system package manager.
 
 ### Docker
 
@@ -496,6 +496,8 @@ Named context shortcuts (e.g. `dcr`, `dck`) live in `~/.config/.user-dots/fish/l
 
 | Tool | Version | Purpose |
 |---|---|---|
+| [uv](https://docs.astral.sh/uv/) | any | Python runner (needed to build Fish from source) |
+| [Rust / cargo](https://www.rust-lang.org/tools/install) | any | Installs Rust-based tools; required to build Fish |
 | [Fish](https://fishshell.com/) | **≥ 4.0** | Shell |
 | [Fisher](https://github.com/jorgebucaran/fisher) | any | Plugin manager |
 | [Starship](https://starship.rs/) | any | Prompt |
@@ -505,7 +507,7 @@ Named context shortcuts (e.g. `dcr`, `dck`) live in `~/.config/.user-dots/fish/l
 
 > [!WARNING]
 > Fish **4.0 or newer is required.** This config uses `test` syntax and other constructs that are incompatible with Fish 3.x. Older versions will produce errors on startup.
-> If you are on an older Fish, run `fish-deps install` or `fish-deps update` — it will build and install the latest Fish from source using git + cargo (requires cargo and uv).
+> Run `fish-deps install` or `fish-deps update` to upgrade — it will install `uv` and `cargo` automatically if missing, then build the latest Fish from source.
 
 ### Recommended