fix(lint): correct four Vale behaviours the skills described wrongly

Each of these would send a user down a path Vale does not support:

Core options placed under a glob header are not scoped to that glob — Vale
rejects them with E201, so the guidance to nest them produced a config that
will not load. The built-in `Vale` style is compiled in, but Vale still
requires StylesPath to exist on disk before it will run, so the "no StylesPath
needed" shortcut fails. The MDX guidance was inverted: under `[formats]
mdx = md` the mapping is what makes MDX lint at all, and it needs the mdx2vast
prerequisite that was never mentioned. And a spelling rule's `ignore` paths
resolve against StylesPath, not against the rule file's own directory, so the
documented relative paths silently matched nothing.

plugins/lint/.apm/skills/vale-config/SKILL.md

@@ -8,7 +8,7 @@ description: >
 
 metadata:
   category: lint
-  version: "0.1.1"
+  version: "0.1.2"
   source_keys:
     - context7-websites-vale-sh
     - house-vale-3-15-2-repro
@@ -19,7 +19,7 @@ metadata:
 - A style in `BasedOnStyles` that is neither built-in nor a directory under `StylesPath` fails hard, not silently: `E100 [loadStyles]`, exit 2, nothing linted.
 - `vale sync` alone does not clear that `E100`. Sync fetches only what the top-level `Packages` key declares, so against a `BasedOnStyles`-only name it reports `Synced 0 package(s)` and exits 0, fetching nothing. Add the style to `Packages`, then sync. A style lints only once it is in both keys — and the reverse case is silent, exiting 0.
 - Only *package* styles need fetching: built-in `Vale`, and any style whose YAML is already committed under `StylesPath`, lint with no `Packages` entry and no sync.
-- `.vale.ini` is order-sensitive: core settings first, then `[formats]`, then glob sections. Anything written below a glob header applies only to files matching that glob.
+- `.vale.ini` order is enforced, not stylistic: put core settings first, then `[formats]`, then glob sections. A core setting (`StylesPath`, `MinAlertLevel`, `Vocab`, `IgnoredScopes`, `SkippedScopes`) written below a `[glob]` header is a hard error — `E201 ... 'StylesPath' is a core option; it should be defined above any syntax-specific options`, exit 2, nothing linted. `Packages` is the exception, and the worse one: below a glob header it is accepted with no error, then ignored — `vale sync` reports `Synced 0 package(s)` and downloads nothing.
 - A rule scoped to `text.frontmatter.<key>` silently matches nothing when the field spans multiple lines in most YAML forms. If you scope a rule to frontmatter, read `references/configuration-reference.md` first.
 
 ## Setup workflow
@@ -34,7 +34,7 @@ metadata:
   [*.md]
   BasedOnStyles = Vale
   ```
-  `Vale` here is the built-in style (`Vale.Spelling`, `Vale.Terms`, `Vale.Avoid`, `Vale.Repetition`) — no download needed, it always works.
+  `Vale` here is the built-in style (`Vale.Spelling`, `Vale.Terms`, `Vale.Avoid`, `Vale.Repetition`): no `Packages` entry and no `vale sync`. It still needs the `StylesPath` directory to exist — declare `StylesPath = styles` without creating `styles/` and even a `Vale`-only config dies with `E201 ... The path '...' does not exist`, exit 2. That is why the previous step creates the directory.
 - [ ] **Add third-party styles** (optional) by declaring them in `Packages`, then activating them in the same or another glob's `BasedOnStyles`:
   ```ini
   Packages = Google, write-good

plugins/lint/.apm/skills/vale-config/references/configuration-reference.md

@@ -25,6 +25,10 @@ Map an unrecognized extension onto a supported one so Vale lints it with the rig
 mdx = md
 ```
 
+`mdx` is the case that matters, because Vale 3.15.2 has no built-in MDX support. The mapping above is not cosmetic: it is what lets `.mdx` files lint with nothing else installed. Leave it out and Vale takes the native MDX path, which shells out to an external `mdx2vast` binary — absent from `PATH`, the run dies with `E100 [lintMDX] Runtime error / mdx2vast not found`, exit 2, and every other file in the same invocation goes unlinted too. Install it with `npm install -g mdx2vast` or take the mapping.
+
+The choice also decides the inline-suppression syntax, and it is inverted between the two: mapped to `md`, `.mdx` takes Markdown's `<!-- vale off -->`; native, it takes `{/* vale off */}`. `vale-run`'s `references/troubleshooting.md` carries the verified matrix.
+
 ## Vocabularies
 
 Reference a named vocabulary (a folder of accept/reject word lists under `StylesPath`) via `Vocab`, then apply styles per glob:
@@ -89,6 +93,8 @@ Only *package* styles need fetching. A style whose YAML rule files are already c
 | Style in `Packages` and synced, but in no glob's `BasedOnStyles` | 0 findings, exit 0 — downloads, never lints, indistinguishable from a clean run |
 | `BasedOnStyles` names an *empty* directory under `StylesPath` | 0 findings, exit 0 — loads and lints nothing; `vale sync` never produces this state |
 | Built-in `Vale`, or a style's YAML committed under `StylesPath` | lints immediately, no `Packages` entry, no sync |
+| Core option (`StylesPath`, `MinAlertLevel`, `Vocab`, `IgnoredScopes`, `SkippedScopes`) below a `[glob]` header | `E201 Invalid value` — `'X' is a core option; it should be defined above any syntax-specific options ([...])`, exit 2 |
+| `Packages` below a `[glob]` header | no error, exit unaffected — parsed as a per-glob rule toggle (`SChecks: {"*.md": {"Packages": false}}` in `ls-config`), so `vale sync` reports `Synced 0 package(s)` and downloads nothing |
 
 ## Frontmatter Scopes
 

plugins/lint/.apm/skills/vale-config/references/sources.md

@@ -11,7 +11,7 @@
 ## house-vale-3-15-2-repro
 
 - **URL:** (house-verified — reproduced locally against the `vale` binary, not an external source)
-- **Description:** Behaviour of Vale 3.15.2 established by running it against purpose-built fixtures in this repo, where vale.sh documents nothing: the `E100 [loadStyles]` / exit-2 failure for a `BasedOnStyles` name absent from `StylesPath`, `vale sync` reporting `Synced 0 package(s)` for a name not declared in `Packages`, the `E201` / exit-2 failure when the `StylesPath` directory does not exist, the exit-0 no-op of an empty style directory, and the `text.frontmatter.<key>` scope matrix across multi-line YAML forms.
+- **Description:** Behaviour of Vale 3.15.2 established by running it against purpose-built fixtures in this repo, where vale.sh documents nothing: the `E100 [loadStyles]` / exit-2 failure for a `BasedOnStyles` name absent from `StylesPath`, `vale sync` reporting `Synced 0 package(s)` for a name not declared in `Packages`, the `E201` / exit-2 failure when the `StylesPath` directory does not exist, the exit-0 no-op of an empty style directory, the `E201` / exit-2 failure when a core option is written below a `[glob]` header (with `Packages` as the silent exception), and the `text.frontmatter.<key>` scope matrix across multi-line YAML forms.
 - **Research doc:** none — house-verified reproduction, not part of the plugin's research corpus (no `plugins/lint/docs/research/` topic file backs this entry)
 - **Contributing files:** SKILL.md, references/configuration-reference.md
 - **Status:** `extracted`