Temporal-validity RFC v1 shipped all 7 goals on main 2026-04-29
(#533/#534/#538/#539/#540), but the implementation PRs deliberately
deferred user-facing docs because (a) the feature is opt-in via
frontmatter — users don't encounter ``as_of`` until they edit — and
(b) PROMOTION-CRITERIA #1 ("no breaking changes for at least 2
release cycles or 1 minor version bump") is not yet met for a
full standalone guide.

This adds the *minimum* surface mentions per
``feedback_doc_update_process.md`` (new CLI flag / MCP tool param
need same-PR reference doc), without inflating into a conceptual
guide. Comprehensive explanation lives in private docs and gets
promoted to ``docs/guides/temporal-validity.md`` after one minor
version bump and a source-of-truth audit.

Surface mentions:

- ``docs/guides/reference.md`` ``mem_search`` parameters table:
  one row for ``as_of`` covering format (``YYYY-MM-DD`` /
  ``YYYY-QN``), default semantics, and opt-in behavior.
- ``docs/guides/reference.md`` ``mem_search`` examples: one
  historical-query example.
- ``docs/guides/reference.md`` post-rerank result-count contract
  blockquote, parallel to the existing ``source_filter`` /
  ``tag_filter`` shrinkage caveat (verbatim from the
  ``mem_search`` docstring).
- ``docs/guides/reference.md`` CLI quick-reference: one
  ``mm search --as-of`` line + a ``mm recall`` Validity-column
  parenthetical.
- ``docs/guides/mcp-clients.md`` tool inventory: ``mem_search``
  row gains an ``optional as_of for temporal-validity queries``
  parenthetical (matches the abstraction level of the rest of
  the row).

``README.md`` and ``packages/memtomem/README.md`` features lists
deliberately not touched — those bullets are positioning at the
"what is memtomem" level, and a per-parameter mention would be
out of scale. Will be revisited if temporal-validity becomes a
positioning differentiator after the v2 supersession layer
lands.

Source-of-truth verification (per
``feedback_docs_as_tests.md``):

- ``mem_search(as_of=...)`` →
  ``packages/memtomem/src/memtomem/server/tools/search.py:38``
- ``mm search --as-of`` →
  ``packages/memtomem/src/memtomem/cli/search.py:22``
- ``mm recall`` Validity column (conditional) →
  ``packages/memtomem/src/memtomem/cli/memory.py:163-179``
- Result-count contract wording matches the docstring at
  ``server/tools/search.py:65-68`` verbatim.

Co-Authored-By: Claude <[email protected]>