feat(types)!: drop the blob column type (ADR-0005 Amendment 2)

blob was a dead-end: declarable but never fillable (no literal in either
mode, seed-unsupported), so a blob column could only ever hold NULL. Remove
Type::Blob + Value/CellValue::Blob + the base64 CSV path + the grammar slot
+ completion/render/type-change/seed handling + the binder refusal (whose
message also carried a user-facing "DSL" copy-rule bug). The vocabulary is
now nine types; base64 stays (clipboard OSC-52).

Backward compat is the ADR-0015 migration framework's first real use: a
v1->v2 format bump (CURRENT_SCHEMA_VERSION across serializer/parser/skeleton)
with a migrator that rewrites `type: blob` -> `type: text`, and a forced .db
rebuild from the migrated text when a blob column was actually converted
(the stale .db keeps a STRICT BLOB engine column). Conversion to text is
non-destructive and CSV-free. Covered by a full-stack integration test and a
Tier-4 PTY test that opens a real legacy v1-blob project.

Also sweeps the nine-type vocabulary through CLAUDE.md, requirements.md, the
website (type reference, seed doc, highlight grammar), and the ADR-0030/0033/
0035 cross-references; CHANGELOG Removed entry; handoff-79.

BREAKING CHANGE: the `blob` column type is removed. Existing projects that
declared a blob column are migrated on first open (the column becomes text;
the original project.yaml is kept as a .v1.bak).

src/completion.rs

@@ -631,7 +631,7 @@ pub fn candidates_at_cursor_with_in_mode(
     // Source 1.5: type-name candidates when the walker expects
     // a column-type slot. Type names are a closed set sourced
     // from `Type::all()` (ADR-0005 declaration order:
-    // text/int/real/decimal/bool/date/datetime/blob/serial/
+    // text/int/real/decimal/bool/date/datetime/serial/
     // shortid). The walker surfaces this as
     // `Expectation::Ident { source: Types }`.
     let type_names: Vec<String> = if expected.iter().any(|e| {
@@ -2309,7 +2309,7 @@ mod tests {
     #[test]
     fn type_slot_offers_full_type_vocabulary_when_partial_empty() {
         // After `add column to T: Name (` the parser expects
-        // a column type. With no partial typed, all ten types
+        // a column type. With no partial typed, all nine types
         // from `Type::all()` are offered in declaration order.
         let cs = cands("add column to T: Name (", 23);
         assert_eq!(
@@ -2322,7 +2322,6 @@ mod tests {
                 "bool".to_string(),
                 "date".to_string(),
                 "datetime".to_string(),
-                "blob".to_string(),
                 "serial".to_string(),
                 "shortid".to_string(),
             ],