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).

CLAUDE.md

@@ -58,8 +58,8 @@ Current decisions at a glance (each backed by an ADR):
   `[temp]`-marker / contents-allowlist guards. Anything
   unexpected → refuse, never delete the wrong thing.
 - **Types:** `text`, `int`, `real`, `decimal`, `bool`, `date`,
-  `datetime`, `blob`, `serial`, `shortid`. Compound primary keys
-  supported. No real UUIDs (ADR-0005). FK column type
+  `datetime`, `serial`, `shortid`. Compound primary keys
+  supported. No real UUIDs; `blob` dropped (ADR-0005 Amendment 2). FK column type
   compatibility via `Type::fk_target_type()` — `serial → int`,
   `shortid → text`, others identity (ADR-0011).
 - **Safety:** append-only `history.log` for replay and scripting