tasks(arch): adopt taskgraph for architecture work — blocker tasks for deferred OQs, level mapping, status fixes

Establishes the tasks/architecture/ blocker-task half of the Safe Exit
protocol. Each deferred OQ now has an external-trigger tracker task
representing its unblocking condition, and the OQ's Blocked on field names
the tracker task ID — closing the gap where the deferral field existed but
the task-graph half was unenforced.

Changes:
- Add 6 external-trigger tracker tasks for the deferred OQs (OQ-09, 10, 32,
  41, 44, 46) under tasks/architecture/, tagged [external-trigger, deferred-oq]
- Add structured Blocked on field to OQ-09 and OQ-10 (previously used legacy
  'deferred' status with the reason in the Resolution prose); index now
  surfaces all 6 deferred OQs with concrete conditions, no placeholders
- Document the architecture-task level mapping (level: implementation for
  ADRs/specs, decomposition for spec-to-ADR breakdown, planning for backlog
  seeding, research/review direct fits) and the deferred-OQ blocker-task
  pattern in docs/sdd_process.md
- Mark architecture/safe-exit-blocker-task-mechanism and
  architecture/oq-09-10-blocking-conditions completed (implemented by this pass)
- Fix 4 pre-existing ADR-050 implementation tasks: status: done → completed
  (taskgraph enum is 'completed', not 'done') — taskgraph validate now passes
  for all 100 tasks

docs/architecture/questions/009-wasm-target-boundaries.md

@@ -4,5 +4,6 @@
 - **Status**: deferred
 - **Door type**: One-way (when applicable)
 - **Priority**: low
+- **Blocked on**: A concrete server-side WASM use case, or a deliberate confirmation that WASM stays a client-side design constraint. Tracked as `architecture/oq-09-wasm-server-use-case` in `tasks/architecture/`.
 - **Resolution**: Not an active question — WASM compatibility is a design constraint (see ADR-009, overview.md design principles), not a deliverable. Specific WASM targeting decisions will be made when individual crates are implemented. **BiStream being a trait preserves the *client-side* stream door** — a browser can implement BiStream over WebTransport streams. **The *server-side* dispatch door is NOT preserved by ADR-007 and is a known, accepted closure**: `Connection` is a concrete quinn-bound struct (not a trait), the accept loop uses `tokio::spawn` (tokio does not run on WASM), and the call-protocol dispatch internals (`PendingRequestMap`, `CallAdapter`) use tokio `oneshot`/`mpsc` channels. A WASM server-side peer would require a `Connection` trait and a runtime-abstracted accept loop — not planned. The browser path is client-side via a JS SDK, not server-side Rust-to-WASM. This is an explicit one-way door, not an oversight.
 - **Cross-references**: ADR-007, ADR-009

docs/architecture/questions/010-git-adapter-scope-smart-protocol-only-or-full-server.md

@@ -4,5 +4,6 @@
 - **Status**: deferred
 - **Door type**: Two-way
 - **Priority**: low
+- **Blocked on**: Speccing the alknet-git crate — resolve this when that crate is specified, not deferred past it. Tracked as `architecture/oq-10-git-adapter-spec` in `tasks/architecture/`.
 - **Resolution**: Deferred per the cleanup plan. Start with git smart protocol over QUIC streams. ERC721 integration and full server capabilities are additive. **Composability fork (review #002 W18)**: whether git operations are registered in the `OperationRegistry` and callable via `env.invoke()`, or only available as raw smart protocol on `alknet/git`, is a separate decision from ERC721 scope. The path of least resistance (raw smart protocol only) forecloses agent composition of git operations — an agent handler that wants to compose `git/clone` cannot, because there's no `OperationSpec`, no `Handler`, no registration. To make git composable, a call-protocol projection (a set of `HandlerRegistration` bundles wrapping git operations behind the registry) must be built alongside or instead of the raw handler. Resolve this when speccing alknet-git, not deferred past it.
 - **Cross-references**: ADR-001