docs: split user and developer docs (#93)

docs/releases/v0.4.0.md

@@ -65,7 +65,7 @@ manifest. The next mutation against that table fails with
 `ExpectedVersionMismatch`. Most validation runs before any Lance write,
 so single-statement mutations are unaffected; the narrow path is
 multi-statement queries with late-op failures. Tracked as a follow-up;
-see [docs/runs.md](../runs.md#known-limitation-mid-query-partial-failure-on-the-same-table)
+see [docs/dev/runs.md](../dev/runs.md#known-limitation-mid-query-partial-failure-on-the-same-table)
 for the workaround.
 
 ## Upgrade notes

docs/releases/v0.4.1.md

@@ -19,7 +19,7 @@ mutation proceeds normally.
   HEAD on every staged table is untouched and the next mutation
   proceeds normally. A narrowed residual remains at the
   finalize→publisher boundary (multi-table `commit_staged` is not
-  atomic with the manifest commit) — see [docs/runs.md](../runs.md)
+  atomic with the manifest commit) — see [docs/dev/runs.md](../dev/runs.md)
   "Finalize → publisher residual" for details.
 - **D₂ parse-time rule**: a single mutation query is either
   insert/update-only or delete-only. Mixed → rejected with a clear
@@ -40,8 +40,8 @@ mutation proceeds normally.
   `restore_coordinator` API and `CoordinatorRestoreGuard` are removed
   from `mutation.rs`. (`merge.rs` keeps its own swap pattern; that's
   a separate workflow.)
-- **`docs/invariants.md` §VI.25** flips from `aspirational/open` to
-  `upheld for inserts/updates`. The within-query read-your-writes
+- **`docs/dev/invariants.md` mutation atomicity / read-your-writes status**
+  flips from `aspirational/open` to `upheld for inserts/updates`. The within-query read-your-writes
   guarantee is now load-bearing for the publisher CAS contract.
 
 ## Behavior changes
@@ -105,29 +105,29 @@ mutation proceeds normally.
 - `Cargo.toml` (workspace) + `crates/omnigraph/Cargo.toml` — added
   `datafusion = "52"` direct dep (transitively pulled by Lance
   already; required for `MemTable`).
-- `docs/runs.md` — removed "Known limitation" section; documented
+- `docs/dev/runs.md` — removed "Known limitation" section; documented
   the new accumulator + D₂ + LoadMode::Overwrite residual.
-- `docs/invariants.md` — §VI.25 status flipped to `upheld for
-  inserts/updates`.
-- `docs/architecture.md` — added "Mutation atomicity — in-memory
+- `docs/dev/invariants.md` — mutation atomicity / read-your-writes status
+  flipped to `upheld for inserts/updates`.
+- `docs/dev/architecture.md` — added "Mutation atomicity — in-memory
   accumulator" subsection; refreshed the engine + state
   diagrams to drop `RunRegistry` and add `MutationStaging`.
-- `docs/execution.md` — rewrote the mutation flow sequence diagram
+- `docs/dev/execution.md` — rewrote the mutation flow sequence diagram
   for the staged-write path; updated the `LoadMode` table to call
   out per-mode commit semantics; rewrote `load` vs `ingest`.
-- `docs/query-language.md` — documented the D₂ parse-time rule.
-- `docs/errors.md` — added the D₂ `BadRequest` rejection path.
-- `docs/storage.md` — dropped the live `_graph_runs.lance` reference
+- `docs/user/query-language.md` — documented the D₂ parse-time rule.
+- `docs/user/errors.md` — added the D₂ `BadRequest` rejection path.
+- `docs/user/storage.md` — dropped the live `_graph_runs.lance` reference
   from the layout diagram and prose.
-- `docs/branches-commits.md` — moved `__run__<id>` to a legacy note;
+- `docs/user/branches-commits.md` — moved `__run__<id>` to a legacy note;
   removed `publish_run` from the publish-trigger list.
-- `docs/audit.md` — current `_as` API list refreshed; legacy
+- `docs/user/audit.md` — current `_as` API list refreshed; legacy
   `RunRecord.actor_id` moved to a historical note.
-- `docs/constants.md` — marked the run registry / branch-prefix rows
+- `docs/user/constants.md` — marked the run registry / branch-prefix rows
   as legacy.
-- `docs/cli.md` — replaced the legacy `omnigraph run *` quickstart
+- `docs/user/cli.md` — replaced the legacy `omnigraph run *` quickstart
   block with `omnigraph commit list/show`.
-- `docs/testing.md` — extended the `runs.rs` row to cover the new
+- `docs/dev/testing.md` — extended the `runs.rs` row to cover the new
   staged-write contract tests; added the `staged_writes.rs` row.
 - `AGENTS.md` (CLAUDE.md symlink) — updated the atomic-per-query
   description and the L2 capability matrix row.