Mirrors the settings-doc gen pattern. Each code's category,
description, and (for errors) bespoke exit code now lives next to
its `pub const` declaration in `crates/aube-codes/src/{errors,warnings}.rs`
as part of a `CodeMeta` entry in `ALL` — one source of truth instead
of two (registry + handwritten markdown). The doc page becomes a
build artifact regenerated on every `mise run render`, and a
self-test gates that every code carries a non-empty description.

* Lift `ALL` from `&[(&str, &str)]` to `&[CodeMeta]` carrying name,
  category, description, exit_code (None for warnings, Option<i32>
  for errors). The `pub const ERR_AUBE_*` / `pub const WARN_AUBE_*`
  declarations stay (call sites consume them); `ALL` references the
  same constants so a rename flows through both with no drift.
* Collapse `EXIT_TABLE` into the same registry — `exit::exit_code_for`
  now walks `errors::ALL`. Tests still gate uniqueness, [10, 125]
  range, and round-trip; the duplicate `EXIT_TABLE` constant is gone.
* New `crates/aube-codes/src/bin/generate_error_codes_docs.rs` walks
  the registries, groups by category in declaration order, and writes
  `docs/error-codes.md`. Wired into `mise run render` after the
  settings doc gen.
* Self-tests now reject codes with empty descriptions or empty
  categories, and reject any warning that accidentally got an
  `exit_code` set (warnings don't change exit status).

rustfmt's default 100-col width wraps long const lines into a two-line
`name: &str =\n    "name";` shape that breaks the visual rhythm of the
flat const list. Skipping fmt on the five affected entries keeps them
one line each so the file scans as a single declaration table.

Mirrors the benchmarks pattern (`benchmarks/results.json` →
`docs/benchmarks.data.ts` → `<BenchChart>`). The hand-rolled
markdown table was static and ungrep-friendly past ~85 entries; an
interactive Vue component lets users search by name/description and
filter by category.

* `generate-error-codes-docs` now emits `docs/error-codes.data.json`
  instead of markdown. Schema documented inline; hand-rolled JSON
  emitter so `aube-codes` stays dep-free.
* `docs/error-codes.data.ts` — VitePress build-time data loader,
  same shape as `docs/benchmarks.data.ts`.
* `docs/.vitepress/theme/ErrorCodesTable.vue` — searchable +
  category-filterable table with sticky controls. Two mounts on
  `/error-codes` (one for errors, one for warnings) keep their own
  filter state. Inline-code is rendered from backticks in the
  registry's description strings via a small one-pass substitution.
* `docs/error-codes.md` is now hand-written prose + two component
  mounts; it's no longer a generated artifact. Only the underlying
  JSON is regenerated from the registry.
* `docs/package.json` adds `error-codes:gen` and chains it into
  `data:gen` so `npm run docs:dev` and `docs:build` always rebuild
  the JSON before VitePress picks it up.

The dep-free posture was overly precious — `serde_json` is already
in 8 of 10 aube crates, so adding it to `aube-codes` doesn't grow
the compile graph. `CodeMeta` derives `Serialize` and the generator
hands the registry plus the first-seen-order category lists straight
to `serde_json::to_string_pretty`. Less code, no escape edge cases,
and the schema travels with the type definition.

cargo-machete on the test-linux job correctly flagged `aube-codes`
as unused in `aube-scripts`, `aube-workspace`, and `aube-store`.
These crates only mention codes via `#[diagnostic(code(ERR_AUBE_X))]`
attributes, where miette treats the `code(...)` argument as an
identifier token rather than a symbol reference, so the dependency
never actually resolves a symbol from `aube-codes`.

Drop the dep in all three Cargo.tomls and leave a comment in each
explaining why the codes are still legal but the crate-level dep
isn't needed. Validation that diagnostic-attribute names exist in
`aube_codes::errors::ALL` is a workspace-wide concern, not
something each consumer should pretend to enforce via a dummy
dep declaration.

Verified locally: `cargo machete` is now clean.