[T432733 Server Side Edit Suggestions - Linked Artifacts Cache precompute job](https://phabricator.wikimedia.org/T432733)

This EditSuggestionCounts/ directory contains 'throwaway' code that
is meant to only exist here for the first couple of quarters of WMF FY2026-2027.

Rather than hardcoding an individual job specifically for EditSuggestionCounts
Linked Artifacts Cache warming (precompute), we can generalize a job for other
LAC usages.

Another PoC here: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/EventBus/+/1305805

This code should not exist here beyond
[T430712 [EPIC] Launch controlled experiment of surfacing suggestion counts on articles to logged-in editors](https://phabricator.wikimedia.org/T430712).
If that experiment confirms that we will continue with the Server Side Edit Suggestions project,
then this responsibility should move elsewhere.

### VisualEditorEditSuggestionCounts config

An array controlling the EditSuggestionCounts feature. Read by both sides of the
feature — the precompute path (which warms the LAC after each edit) and the
product read path (which fetches precomputed counts from LAC for the page being
viewed).

**`enabled`** — `bool`, default `false`
: Whether the feature is enabled on this wiki. When `false`, the feature is off:
  nothing is precomputed and the product code does not fetch counts. Set per
  wiki.

**`linked_artifact_url_template`** — `string`
: LAC endpoint URL template. The `{wiki_id}`, `{page_id}`, and `{revision_id}`
  placeholders are substituted (rawurlencoded) per revision. Default:
  `https://linked-artifacts.discovery.wmnet:30443/revisions/v1/edit_suggestions_counts/{wiki_id}/{page_id}/{revision_id}`

**`linked_artifact_precompute_timeout`** — `int`, default `50`
: HTTP request timeout, in seconds, for the precompute call to LAC. Set it above
  the LAC lambda timeout for this table. If the request times out first, LAC does
  not store the counts, and the job fails and is retried.

**`namespaces_enabled`** — `int[]`, default `[ 0 ]`
: Page namespaces the feature is enabled for. Only pages in these namespaces are
  in scope. An empty array `[]` means **all** namespaces.

**`page_sample_proportion`** — `float`, default `1.0`
: Proportion of pages the feature is enabled for, in `[0.0, 1.0]`. Deterministic
  per page. `1.0` = every page, `0.0` = none. Out-of-range values throw
  `InvalidArgumentException`.

#### Notes

- **Sampling is deterministic and per-page.** Whether the feature is enabled for
  a page is a stable hash of `(wiki_id, page_id)`, so a page is always in the
  same cohort — its in/out decision doesn't change between requests, and both the
  precompute and read paths agree.