Prefix HSSS result IDs with Variant_ instead of NGS_SNP.

[jbrestel]

Makes the HSSS plugins emit VariationRecordClass source_ids, by changing the ApiCommon
cohort default for the result-ID prefix:

-highspeedsnpsearchconfig_idPrefix: NGS_SNP.
+highspeedsnpsearchconfig_idPrefix: Variant_

Paired with the separator fix in ApiCommonWebService #20, this produces IDs of the form
Variant_<sequence>_<location> — which is what the record class has always actually held,
and what ApiCommonModel #212 renames the record to match.

Merge with ApiCommonModel #212 and ApiCommonWebService #20. The prefix, the
separator, and the record-class naming are one change spread across three repos; any two
of the three without the third leaves the HSSS searches emitting IDs the record class
won't resolve.

Scope of the cohort default

This is an ApiCommon cohort default, so it applies to every project in the cohort, not
just PlasmoDB. That is safe because no project has a live snp or chip search — those
imports are commented out in the shared apiCommonModel.xml. The chip default
(highspeedchipsnpsearchconfig_idPrefix: 'NULL') is left alone: that path is equally dead
but out of scope here.

The release note was pulled from this PR

This PR previously carried a news.xml entry for the corrected density and dN/dS
statistics. It has been reverted (965009fdd reverts a039aeee9) because its date
attribute was an unresolvable placeholder — the news page would have rendered TBD - set to the release date literally, and inventing a date was not an option.

The drafted text is preserved in this branch's history and can be recovered with
git show a039aeee9 when the release date is known. It should return as its own PR at
that point. Nothing about the statistics themselves changed; only the announcement is
deferred.

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Related PRs

The variants work spans four repos. These four merge together — ApiCommonModel's record rename is a contract the other three depend on by name:

• ApiCommonModel Rename the Variation record to Variant; add a precomputed SNV characteristics search ApiCommonModel#212 — record rename + precomputed SNV characteristics search
• ApiCommonWebService Fix SNV density and dN/dS in the sample-set SNV search, and revive its test suite ApiCommonWebService#20 — density and dN/dS fixes, test-suite repair
• ApiCommonWebsite Prefix HSSS result IDs with Variant_ instead of NGS_SNP. #310 — HSSS result-ID prefix (NGS_SNP. → Variant_)
• web-monorepo Show the Variant record id without the record-type prefix web-monorepo#1841 — record-heading override, filename tracking the rename

Coupling worth knowing when sequencing the merges: #1841's customization is resolved by recordClass.fullName, so without #212 it matches nothing and the override silently stops applying — no error, just the default heading back. #310's prefix and #20's separator together produce the ids #212's record class resolves; any two without the third leaves HSSS emitting ids the record class rejects.

Related but independent, cherry-picked onto master — merge before the four above:

• EbrcModelCommon Optional dataset gate for presenter template injection (partial-appDb builds) EbrcModelCommon#131 — optional dataset gate for presenter template injection. Not part of the variants work; needed to build a site against a partial appDb.

The release note originally in #310 has been deferred (reverted in 965009fdd) because its date attribute was an unresolvable placeholder. Recover the drafted text with git show a039aeee9 in ApiCommonWebsite and re-PR it once the release date is known.