Dev loop: point dl-next and pixi run dl at the Rust build #268

Follow-up named in PR #260: after the cutover, the dev-loop names still run Python.

• Host: ./dev.sh installs the Python tree editable as dl-next/aid-next (uv). The released dl is now Rust 0.1.0, so -next no longer previews the build that ships.
• Container: pixi run dl resolves to the editable Python install ([tool.pixi.pypi-dependencies] devlaunch = { path = ".", editable = true }), not rust/target/*/dl.

The change

• dev.sh: build rust/ (cargo build --release -p dl -p aid) and symlink dl-next/aid-next at the Rust binaries — the wf-next trade (compiled copy, moves on rebuild) replaces the editable trade, which Rust cannot offer. --version provenance: released prints dl 0.1.0; decide what a dev build prints now that divergence row 16 dropped the (dev, editable from …) suffix — a -dev build marker in the version line is the natural replacement, added deliberately, not by drift.
• Devcontainer: point pixi run dl/pixi run aid tasks at cargo-built binaries (or a pixi run dl-build task first); the devpod-on-PATH reasoning in AGENTS.md carries over unchanged.
• AGENTS.md/CLAUDE.md: rewrite the "Two installs" and "Inside the devcontainer" sections — the editable-install premises ("no build step", "half-finished edit is live", "git stash restores a working pixi run dl") are all false for a compiled build.
• Moves with its own test, per the PR note: a check that dl-next --version ≠ released dl --version provenance, so the two names provably name different builds.

Until this lands, the working-tree preview of the shipping implementation is cargo run -p dl under rust/. Related: #267 (whose Python deletion removes the editable install this replaces — landing this first avoids a window where dev.sh is broken).