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/friendly/keys.rs

@@ -425,7 +425,6 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     ("hint.value_literal_slot", &[]),
     ("hint.ambient_typing_name_then", &["next"]),
     // Per-column-type value-slot hints (ADR-0024 §Phase D).
-    ("hint.value_slot_blob", &[]),
     ("hint.value_slot_bool", &[]),
     ("hint.value_slot_date", &[]),
     ("hint.value_slot_datetime", &[]),

src/friendly/strings/en-US.yaml

@@ -395,7 +395,7 @@ help:
                                                            without running it (advanced SQL)
   # Type reference, appended after the command list.
   types_reference: |
-    Types: text, int, real, decimal, bool, date, datetime, blob, serial, shortid
+    Types: text, int, real, decimal, bool, date, datetime, serial, shortid
     Auto-generated types (serial, shortid):
       serial   — integer that auto-fills with the next sequence value
                  (MAX(col)+1) on insert. Outside a primary key it carries
@@ -714,7 +714,6 @@ hint:
   value_slot_text: "Type a quoted string (e.g. 'Alice') or null"
   value_slot_date: "Type a quoted date as 'YYYY-MM-DD' or null"
   value_slot_datetime: "Type a quoted datetime as 'YYYY-MM-DD HH:MM:SS' or null"
-  value_slot_blob: "Type a quoted blob literal or null"
   # Serial / shortid in `values (…)` form: the user must enter
   # something at this position (no "skip column" syntax). `null`
   # is the auto-fill path (ADR-0018: serial / shortid columns