feat(research, registry, cli, runner): C29 register seam -- description gate, store-boundary doc gate, authored root docs

Iteration 3 of the self-description plan, tasks 1-3 (checkpoint commit
mid-iteration; the register e2e, the op-script doc slot, and the full
gates follow):

- aura-research: DocFault::BadDescription { subject, fault }; a present
  document description passes doc_gate in validate_process /
  validate_campaign (absent is never a fault and stays byte-identical);
  prose arm in doc_fault_prose; tests incl. content-id participation.
- aura-registry: the store boundary gates admission -- the public
  put_blueprint parses the canonical bytes and walks root + named
  nested composite docs (None refuses like ""), refusing via
  UndescribedComposite { name, fault } / MalformedBlueprint; the raw
  write survives as private put_blueprint_unchecked (store-mechanics
  tests + the never-retroactive witness: doc-less pre-C29 entries stay
  readable). Registry-internal seeders triaged junk-vs-real.
- authored root docs: the 4 example blueprints + their 4 open-fixture
  twins, the scaffold starter template, the scaled_signal and hl_signal
  inline fixtures, and the three programmatic member.rs builders
  (breakout, meanrev, hl_channel) via GraphBuilder::doc -- mechanical
  propagation of the authored lines.

Recovery note: the implement run's task 3 discarded tasks 1+2's edits
in three files via a file-level checkout (the issue-#23 guard shape);
the loop's boundary snapshot caught it and the content was restored
from recovery snapshot 11a6ae2, then re-verified (research 81 green,
registry 51 green, cli 58/59).

Known-open at this checkpoint: the op-script register test is red --
op-built composites have no doc surface (#125 scope cut); the op
vocabulary grows the anticipated doc slot in the next task of this
iteration (decision logged on the issue).

refs #316

crates/aura-cli/tests/cli_run.rs

@@ -2182,7 +2182,7 @@ const HL_RANGE_CLOSED_BLUEPRINT: &str = r#"{
     "output": [{"node":0,"field":0,"name":"bias"}]
   }
 }"#;
-const HL_SIGNAL_OPEN_BLUEPRINT: &str = r#"{"format_version":1,"blueprint":{"name":"hl_signal","nodes":[{"primitive":{"type":"SMA","name":"fast"}},{"primitive":{"type":"SMA","name":"slow"}},{"primitive":{"type":"Sub"}},{"primitive":{"type":"Bias","name":"bias","bound":[{"pos":0,"name":"scale","kind":"F64","value":{"F64":0.5}}]}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"high","targets":[{"node":0,"slot":0}],"source":"F64"},{"name":"low","targets":[{"node":1,"slot":0}],"source":"F64"}],"output":[{"node":3,"field":0,"name":"bias"}]}}"#;
+const HL_SIGNAL_OPEN_BLUEPRINT: &str = r#"{"format_version":1,"blueprint":{"name":"hl_signal","doc":"high/low SMA difference clamped into a directional bias","nodes":[{"primitive":{"type":"SMA","name":"fast"}},{"primitive":{"type":"SMA","name":"slow"}},{"primitive":{"type":"Sub"}},{"primitive":{"type":"Bias","name":"bias","bound":[{"pos":0,"name":"scale","kind":"F64","value":{"F64":0.5}}]}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"high","targets":[{"node":0,"slot":0}],"source":"F64"},{"name":"low","targets":[{"node":1,"slot":0}],"source":"F64"}],"output":[{"node":3,"field":0,"name":"bias"}]}}"#;
 
 /// Property (#231 task 4 quality follow-up): `aura run` over a multi-column
 /// blueprint with NO `--real` (the synthetic default) refuses through the