docs(arch): decompose open-questions.md into per-OQ files under questions/

The monolithic open-questions.md (1310 lines, 47 OQs) was large enough to be
unmanageable, with high size variance (OQ-42 at 220 lines next to OQ-06 at 8).
Decomposed into one file per OQ under docs/architecture/questions/ (NNN-slug.md,
mirroring the ADR convention), with open-questions.md retained as the index:
theme-grouped tables plus a cross-theme Deferred/Blocked section that surfaces
the 6 deferred OQs with their Blocked-on conditions inline (the safe-exit
visibility surface). Per-OQ content moved verbatim; all 62 inbound links stay
valid (none used anchors). README's curated OQ summary dropped (now redundant
with the index tables).

Also seeds tasks/architecture/ with this task plus two follow-ups found during
the decompose: OQ-09/10 missing structured Blocked-on fields, and the
tasks/architecture/ blocker-task half of the Safe Exit protocol being
unenforced.

tasks/architecture/oq-09-10-blocking-conditions.md

@@ -0,0 +1,46 @@
+---
+id: architecture/oq-09-10-blocking-conditions
+name: Add explicit Blocked on conditions to OQ-09 (WASM) and OQ-10 (Git Adapter)
+status: pending
+depends_on: []
+scope: small
+risk: low
+impact: local
+level: architecture
+---
+
+## Description
+
+During the open-questions.md decompose (July 2026), I found that OQ-09 (WASM
+Target Boundaries) and OQ-10 (Git Adapter Scope) use the legacy `deferred`
+status without a structured `Blocked on:` field. They predate the formalized
+`deferred(scope)` + blocking-condition pattern established by ADR-009's Safe
+Exit protocol.
+
+The four newer deferred OQs (OQ-32, OQ-41, OQ-44, OQ-46) all carry an explicit
+`Blocked on:` condition. OQ-09 and OQ-10 do not — their deferral reason lives
+in the Resolution prose, not in a structured field.
+
+This matters because the new `open-questions.md` index has a "Deferred / Blocked"
+section that surfaces `Blocked on:` inline as the safe-exit visibility surface.
+OQ-09 and OQ-10 currently render as "_(no explicit blocking condition recorded
+— see full file)_" in that section, which weakens the visibility guarantee.
+
+## Work
+
+Either:
+- Add a `Blocked on:` field to each (e.g., OQ-09: "blocked on: a concrete
+  server-side WASM use case — currently a design constraint, not a
+  deliverable"; OQ-10: "blocked on: speccing alknet-git — resolve when that
+  crate is specified, not deferred past it"), or
+- Reframe them as `deferred(scope)` if the original `deferred` status was
+  imprecise, and confirm the blocking condition from the Resolution text.
+
+The decision content stays unchanged — this is a metadata-structure fix, not a
+re-resolution.
+
+## Verification
+
+The "Deferred / Blocked" section of `docs/architecture/open-questions.md` should
+show a concrete blocking condition for OQ-09 and OQ-10 instead of the "no
+explicit blocking condition recorded" placeholder.