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/v0.4.2.md

@@ -1,115 +0,0 @@
-# Omnigraph v0.4.2
-
-Omnigraph v0.4.2 is a concurrency, admission-control, and release-hygiene
-release. It removes the server-global write lock, lets disjoint writers make
-progress concurrently, adds per-actor admission limits, hardens branch and
-mutation races with snapshot-isolation fences, and documents the release in
-public open-source terms.
-
-## Highlights
-
-- **Unlocked server engine handle**: the HTTP server now holds the engine behind
-  a shared handle instead of a server-global write lock. Concurrent handlers can
-  call engine APIs directly while the engine serializes only the resources that
-  actually conflict.
-- **Engine-owned writer queues**: same `(table, branch)` writers are serialized
-  by per-table writer queues inside the engine, while disjoint table/branch
-  writes can run concurrently. This narrows contention without relying on route
-  handlers to know storage-level ordering rules.
-- **Per-actor admission control**: mutating HTTP handlers are gated by a
-  `WorkloadController` with per-actor in-flight request and estimated-byte
-  budgets. Rejections use HTTP 429 with `code: too_many_requests` and a
-  `Retry-After` header, so noisy actors back off without blocking unrelated
-  actors.
-- **Admission coverage for all mutating handlers**: `/change`, `/ingest`,
-  `/schema/apply`, branch create/delete, and branch merge now flow through the
-  admission controller. Read-only endpoints are not admission-gated.
-- **Op-kind-aware version checks**: mutation commit-time drift checks distinguish
-  append-like inserts from strict update/delete work. Inserts remain permissive
-  enough for safe concurrent append patterns; updates and deletes get stricter
-  stale-view rejection.
-- **Read-time drift checks for strict mutations**: staged mutations compare the
-  manifest pin captured when the query opened against the manifest snapshot
-  captured under table-queue ownership. If a concurrent writer moved the table
-  after the query read, the stale writer returns a structured
-  `manifest_conflict` 409 instead of staging work computed against an old
-  snapshot.
-- **Inline-delete recovery coverage**: delete-only mutations still use Lance's
-  inline delete path, but their recovery sidecar is now written before the
-  manifest-version rejection path can return. If a delete moves Lance HEAD and a
-  concurrent manifest update makes the query stale, the next read-write open can
-  roll the residual back rather than leaving a head-ahead-of-manifest table.
-- **Branch-operation race hardening**: branch creation and branch merge avoid
-  coordinator swap-restore races that could expose the wrong active branch to
-  concurrent work. Concurrent branch merges are serialized by a merge mutex.
-- **Branch-merge target revalidation**: merges re-check target table versions
-  after acquiring target write queues. A stale merge plan returns a structured
-  conflict instead of overwriting concurrent target-branch changes or adopting a
-  source table over newly appended target rows.
-- **Schema refresh deadlock fix**: recovery refresh releases the write guard
-  before schema reload, preventing a refresh/schema-apply deadlock.
-- **Lean admission API**: removed the unused global rewrite admission pool,
-  `service_unavailable` error variant, related 503 documentation, and benchmark
-  flag. The public server surface now reflects only admission behavior that is
-  wired to handlers.
-- **Open-source release hygiene**: this release adds guidance for public-facing
-  documentation, release notes, and version bumps. Release docs now avoid
-  private issue tracker references and use stable public descriptions instead.
-
-## Behavior changes
-
-- Disjoint mutating HTTP requests can now make progress concurrently instead of
-  queueing behind one process-wide engine write lock.
-- Mutating handlers may return HTTP 429 when an actor exceeds per-actor in-flight
-  or estimated-byte budgets. Clients should respect `Retry-After` and retry
-  later.
-- Concurrent update/delete and merge races now return structured
-  `manifest_conflict` 409 responses in more stale-view cases instead of relying
-  on later publisher-CAS detection or allowing a stale plan to proceed.
-- Concurrent branch merge × change on the same target branch may return either
-  success or a clean 409 conflict, depending on which operation wins the queue.
-- `OMNIGRAPH_GLOBAL_REWRITE_MAX` is no longer recognized. Remove it from
-  deployment manifests; use the per-actor in-flight and byte-budget admission
-  settings for the currently wired server controls.
-
-## Upgrade Notes
-
-- No repository migration is required. Existing v0.4.1 repos can be opened
-  directly with v0.4.2.
-- Clients should treat `manifest_conflict` 409 responses as retryable stale-view
-  conflicts. This was already the documented contract, but this release uses it
-  in more concurrent-write paths.
-- Clients should handle HTTP 429 from every mutating endpoint, not only
-  `/change`. Honor the `Retry-After` header.
-- Operators should remove stale references to global rewrite admission and 503
-  rewrite-pool exhaustion from local runbooks.
-- If you maintain public docs or release notes, use public identifiers and
-  user-facing descriptions rather than private tracker IDs.
-
-## Tests added or strengthened
-
-- Regression tests for update read-your-writes under in-process concurrency.
-- HTTP tests for same-key insert snapshots, disjoint `/change` concurrency, and
-  `/ingest` admission 429 + `Retry-After`.
-- Branch-operation regression tests for branch-create swap-restore races,
-  concurrent `/change` + branch-merge interleavings, branch-merge swap-restore
-  races, branch-op matrix coverage, and post-reopen consistency.
-- Failpoint-backed regression coverage for inline-delete recovery sidecar
-  creation before version-mismatch rejection.
-- Admission tests use injectable `WorkloadController` state instead of mutating
-  process environment.
-
-## Included Changes
-
-- Shared server engine state and per-actor admission on mutating endpoints.
-- Per-(table, branch) writer queues and op-kind-aware manifest drift checks.
-- Strict read-time version checks for updates/deletes.
-- Branch create/merge race hardening and branch-merge target snapshot
-  revalidation under queue ownership.
-- Retry-after support for admission rejections and OpenAPI updates for reachable
-  429 responses.
-- Actor-isolation benchmark harness updates for the current admission controller.
-- Removal of the unwired global rewrite admission / 503 server surface.
-- Version bump to `0.4.2` across workspace crates, `Cargo.lock`, and
-  `openapi.json`.
-- Public release-note cleanup and new OSS best-practice guidance in `AGENTS.md`.