refactor(cli)!: split the contributor tool out of the ludic CLI

`ludic help` ended with a section titled "contributing to the toolchain itself",
listing bootstrap, reseed, docs-gen and release tasks. None of that is available
to someone who installed the language — those tasks need the repository — so the
shipped tool was advertising work its user cannot do, in a namespace they have to
read past to find `new` and `run`.

The tasks move to a second program, dev.ludic -> bin/ludic-dev, built from a
checkout and excluded from every release artifact. `ludic` keeps the project and
package commands and nothing else; `ludic dev …` now explains where the tasks
went instead of failing as an unknown command.

What this shook out: the two programs share prelude/build/project/pkg, so the
helpers each had accreted in whichever file first needed them — cc(),
ensure_ludicc, the string functions, title_case, cmd_version — moved to where
both can see them. The argument-shift indirection added for the `dev` namespace
is gone with the namespace, so commands read argv directly again.

`ludic-dev test` asserts the split rather than trusting it: the staged install
must build a project, and `ludic dev build` there must fail while naming
ludic-dev. install.sh keeps building older tags, whose bootstrap goes through
main.ludic.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

changes/split-dev-cli.md

@@ -0,0 +1,16 @@
+bump: minor
+type: refactor
+**`ludic` is only the language's command line now.** The toolchain's own tasks —
+building the compiler from its IR seed, the regression suites, the docs site,
+releases — moved out of it into a separate `ludic-dev` binary that is built from
+a checkout and is not part of an install.
+
+- **`ludic help` is what a user can actually do**: `new`, `run`, `build`, `test`,
+  `add`, `fmt`, `lsp`, `doctor`, `upgrade`. No section about a repository they do
+  not have. Typing `ludic dev …` says where those tasks went rather than failing
+  as an unknown command.
+- **`ludic dev <task>` becomes `ludic-dev <task>`** for contributors; every task
+  is otherwise unchanged. The bootstrap is now
+  `bin/ludicc tools/ludic-cli/dev.ludic -o bin/ludic-dev && bin/ludic-dev build`.
+- The shipped binary drops from ~880 KB to ~190 KB, since none of the release,
+  docs-generation or bootstrap machinery is linked into it any more.