docs(architecture): Phase 1 spec tree — 7 specs, ADRs 001-006, OQ tracker

- overview/hashing/store-api/backends/gc/ops specs + README index,
  all draft status with YAML frontmatter and cross-referenced ADR/OQ
- ADR-001: substrate posture (store layer alkcall-free = family
  conformance, not deviation) + ops placement decided (feature-gated
  module, no consumer-waited deferral)
- ADR-002: canonical git-blob-sha-256 + key encoding — the declared
  wire-format ADR (one-way door)
- ADR-003: backend contract, sqlite/fs/mem tiers, pure-function
  dispatch, no migration, unknown-length buffering semantics pinned
- ADR-004: exactly two production backends; manifest/path-tree layers
  are consumer-side (the corrected two-vs-three-backends framing)
- ADR-005: pooled CAS, three liveness sources, delete windows with
  pin-before-publish + delete-time arbitration (race closed), no
  ambient scheduling
- ADR-006: whole-blob verification; chunk-tree encodings excluded by
  scoping, not deferred on a paused consumer
- open-questions.md: OQ-BL-01..06 resolved with ADR cross-refs; OQ-07
  /08 externally-owned, OQ-09 deferred(scope) with SDD tracker task
- AGENTS.md: status updated to Phase 1, gix-odb path corrected

Verification: cargo test / clippy -D warnings / fmt --check clean

AGENTS.md

@@ -51,10 +51,10 @@ alk* family, inspired by iroh-blobs' store work but deliberately not a
 fork of it. It sits downstream of alkcall (the call + channels substrate
 its network operations ride, when they exist) and its first planned
 consumer is alkgit (git object storage, where the iroh-blobs hashing
-story collides with git's own object hashes). Status: **Phase 0
-(Exploration)** — `docs/research/` is the working state of the repo;
-`docs/architecture/` does not exist yet and no wire format, API shape,
-or backend trait is decided. The conventions below apply to all work in
+story collides with git's own object hashes). Status: **Phase 1
+(Architecture)** — Phase 0 converged (see `docs/research/phase-0.md`);
+`docs/architecture/` is the working state of the repo (specs, ADRs
+001-006, open-questions tracker). The conventions below apply to all work in
 `src/` and `tests/`. They mirror
 `.opencode/agents/implementation-specialist.md` §Project Conventions and
 are repeated here so they apply to every session.
@@ -152,16 +152,17 @@ corpus replay on stable) is expected — until then ignore fuzzing.
   research findings, POC records, and `phase-0.md` (vision, prior art,
   open questions, converged recommendation). Read it before non-trivial
   work. The SDD process lives in `docs/sdd_process.md`.
-- `docs/architecture/` — does not exist yet (Phase 1 output). When it
-  lands, the SDD process applies: specs describe WHAT, `decisions/`
-  ADRs explain WHY, `open-questions.md` tracks what's unresolved.
+- `docs/architecture/` — exists (Phase 1 in progress: specs draft,
+  ADRs 001-006 accepted, open-questions tracker active). The SDD
+  process applies: specs describe WHAT, `decisions/` ADRs explain WHY,
+  `open-questions.md` tracks what's unresolved.
 - Key prior art (read-only, in the global workspace):
   - **iroh-blobs** — `/workspace/iroh-blobs` (fresh upstream checkout):
     the shape inspiration, specifically its store work (kv + flat file
     backends, bao verification, chunking). Its wire-surface choices
     (tickets, postcard, BLAKE3-only) are the ones we are deliberately
     diverging from.
-  - **gix-odb** — `/workspace/git-oxide/gix-odb`: git's own object
+  - **gix-odb** — `/workspace/gitoxide/gix-odb`: git's own object
     database; the backend alkgit currently plans against and the
     hashing-algorithm baseline git actually uses.
   - **alknet's blobs research** —