docs: audit pass — drop pre-0.7.0 release notes; scrub RFC refs from user docs (#272)

* docs: audit pass — drop pre-0.7.0 release notes; scrub RFC refs from user docs

- Delete the pre-0.7.0 release-notes archive (v0.2.0 … v0.6.2); keep v0.7.0.
- Rewrite every inline "RFC-0NN" citation in docs/user/** into durable
  plain language (the behavior is the contract, not the planning doc):
  cli/index.md, cli/reference.md, clusters/index.md, operations/{maintenance,
  policy,server}.md. Updated the in-page "Scopes & profiles" anchor to match
  the de-RFC'd heading.

No sub-0.7.0 version caveats or stale Lance-version refs were present in
docs/user/**. Dev docs, AGENTS.md, and instruction files are out of scope for
this pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs: second alignment pass — drop residual pre-cluster-only framing

- cli/reference.md: rewrite the server-scope graph-resolution rule — an
  omnigraph-server is always cluster-backed, so GET /graphs always answers and
  --graph is required; the bare-URL path is only the fallback for an
  unavailable/non-omnigraph endpoint (was "a single-graph / flat server …
  uses its bare URL as before").
- embeddings.md: "Direct single-graph serving" → "Direct (--store) access"
  (there is no single-graph serving mode under cluster-only).
- clusters/{config,index}.md: drop the removed --target flag from the
  "--cluster cannot combine with …" clauses.

Verified: no Linear tickets, no RFC refs, no single-graph-as-current, no
--target-as-combinable in docs/user/**.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/releases/v0.4.0.md

@@ -1,88 +0,0 @@
-# Omnigraph v0.4.0
-
-Omnigraph v0.4.0 demotes the Run state machine to commit metadata via the
-publisher's CAS, fixing a write-cancellation hole and reducing the engine's
-surface area.
-
-## Highlights
-
-- **Direct-to-target writes**: `mutate_as` and `load` write
-  directly to the target tables and call
-  `ManifestBatchPublisher::publish` once at the end with
-  `expected_table_versions`. No more `__run__<id>` staging branches, no
-  more `RunRecord` state machine. Cross-table OCC is enforced inside the
-  publisher's row-level CAS on `__manifest`.
-- **Cancellation safety by construction**: a dropped mutation future
-  leaves no graph-level state — only orphaned Lance fragments, reclaimed
-  by `omnigraph cleanup`. The "zombie run" cascade documented in
-  `.context/zombie-run-investigation.md` is gone.
-- **Read-your-writes inside multi-statement mutations**: a `.gq` query
-  that inserts and then references a row in the same statement now sees
-  its own writes via an in-process `MutationStaging` cache, even though
-  no manifest commit happens between ops.
-- **Structured conflict surface**: concurrent writers race through the
-  publisher's CAS; the loser surfaces as
-  `ManifestConflictDetails::ExpectedVersionMismatch { table_key,
-  expected, actual }`. The HTTP server maps this to **409 Conflict** with
-  a structured `manifest_conflict` body so clients can detect-and-retry
-  without parsing the message.
-
-## Removed
-
-This is a breaking release. Pre-0.4.0 / no SLA.
-
-- `omnigraph::db::{RunRecord, RunStatus, RunId}` types and the
-  `_graph_runs.lance` / `_graph_run_actors.lance` Lance datasets.
-- Engine APIs `begin_run`, `begin_run_as`, `publish_run`,
-  `publish_run_as`, `abort_run`, `fail_run`, `terminate_run`,
-  `list_runs`, `get_run`.
-- HTTP endpoints: `GET /runs`, `GET /runs/{run_id}`, `POST
-  /runs/{run_id}/publish`, `POST /runs/{run_id}/abort`. The
-  `RunListOutput` and `RunOutput` schemas are removed from the OpenAPI
-  document.
-- CLI subcommands: `omnigraph run list`, `omnigraph run show`, `omnigraph
-  run publish`, `omnigraph run abort`. Use `omnigraph commit list`
-  reading the commit graph for audit history.
-- Cedar policy actions `run_publish` and `run_abort`. Existing
-  `policy.yaml` files referencing these actions will fail validation —
-  remove the rules; the `change` action covers the equivalent gating.
-
-## Behavior changes
-
-- `mutate_as` / `load` are now **atomic per query, single publish at the
-  end**. A failed mutation leaves the target unchanged with no
-  intermediate manifest commits.
-- The `OmniError::manifest_conflict` shape produced by concurrent
-  writers is now `ExpectedVersionMismatch` (was `MergeConflict::DivergentUpdate`
-  via the run merge path). Clients that match on the conflict body must
-  switch to inspecting `manifest_conflict.table_key/expected/actual`.
-
-## Known limitation
-
-A multi-statement mutation that writes a Lance fragment in op-N and then
-fails in op-N+1 leaves the touched table with Lance HEAD ahead of the
-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/dev/writes.md](../dev/writes.md#mid-query-partial-failure-closed-by-mr-794)
-for the workaround.
-
-## Upgrade notes
-
-- **Stale `__run__*` branches and `_graph_runs.lance`** in legacy v0.3.x
-  repos are *inert* — the engine no longer reads them — but they remain
-  on disk until production cleanup. This release deliberately does not touch
-  legacy bytes.
-- The `is_internal_run_branch` predicate is kept as a defense-in-depth
-  guard against users naming a branch `__run__*`. It will be removed in
-  a follow-up cleanup.
-- External scripts hitting `/runs/*` will now receive 404. Migrate them
-  to `/commits` for audit history; mutation status is implied by the
-  HTTP response on `/change` itself.
-
-## Included Changes
-
-- Demote Run: write directly to target via publisher
-- `ManifestBatchPublisher::publish` accepts per-table
-  `expected_table_versions`