fix(spec): the ui-html-page-div-refused entry states when dev and start compile (#20664)

Closes #20649

The `ui-html-page-div-refused` migration entry's `why:` line no longer
says `dev` and `start` always run `objectstack compile` first. It now
states the condition the CLI implements. The entry file and its
generated copy in `migrations/registry.ts` are the two places the
sentence lived.

Clause-②: no

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_01Sfe5YjBLwB9J3y8fvm2xq1

Co-authored-by: Claude <noreply@anthropic.com>

Author: objectstack-fleet[bot]

.changeset/20649-div-entry-compile-condition.md

@@ -0,0 +1,13 @@
+---
+'@objectstack/spec': patch
+---
+
+fix(spec): the `ui-html-page-div-refused` migration entry states when `dev` and `start` compile (#20649)
+
+Clause-②: no
+
+The entry's `reason`, which `objectstack migrate meta` prints as its `why:`
+line, said `dev` and `start` run `objectstack compile` first. They run it before
+they boot only when the artifact is missing or `--compile` is passed, and `dev`'s
+watch mode runs it when a watched file changes. The text now says so. No schema
+accepts or refuses anything it did not before.

packages/spec/src/migrations/entries/semantic/18.ui-html-page-div-refused.ts

@@ -31,7 +31,9 @@ export const entry: SemanticMigration = {
     'An html page\'s source is a JSX string, not a keyed document: `objectstack migrate meta` '
     + 'rewrites stored metadata by key and cannot rewrite a tag inside authored source, so the '
     + 'move is by hand, and which wrapper keeps a page\'s layout is the author\'s call. '
-    + '`objectstack validate`, `objectstack compile` (which `dev` and `start` run first) and '
+    + '`objectstack validate`, `objectstack compile` (which `dev` and `start` run before they '
+    + 'boot only when the artifact is missing or `--compile` is passed, and `dev`\'s watch mode '
+    + 'when a watched file changes) and '
     + '`objectstack lint` check that source against an SDUI component manifest: the '
     + '`sdui.manifest.json` in the directory the command runs in, then the copy '
     + '`@objectstack/console` ships. The second lookup asked for a file the console package '

packages/spec/src/migrations/registry.ts

@@ -17452,7 +17452,9 @@ const step18: MigrationStep = {
         'An html page\'s source is a JSX string, not a keyed document: `objectstack migrate meta` '
         + 'rewrites stored metadata by key and cannot rewrite a tag inside authored source, so the '
         + 'move is by hand, and which wrapper keeps a page\'s layout is the author\'s call. '
-        + '`objectstack validate`, `objectstack compile` (which `dev` and `start` run first) and '
+        + '`objectstack validate`, `objectstack compile` (which `dev` and `start` run before they '
+        + 'boot only when the artifact is missing or `--compile` is passed, and `dev`\'s watch mode '
+        + 'when a watched file changes) and '
         + '`objectstack lint` check that source against an SDUI component manifest: the '
         + '`sdui.manifest.json` in the directory the command runs in, then the copy '
         + '`@objectstack/console` ships. The second lookup asked for a file the console package '