Mutation gate: remove the three gemini.ts Stryker directives added upstream in #2033 #2201

Problem

upstream/main gained three new Stryker suppression comments in src/api/providers/gemini.ts after #2054's evidence snapshot (#2033 landed 2026-10-18, after the 38-directive/105-mutant reproduction):

• src/api/providers/gemini.ts:183 — Regex,LogicalOperator,ConditionalExpression (octet parsing)
• src/api/providers/gemini.ts:198 — ConditionalExpression (middle octets)
• src/api/providers/gemini.ts:647 — StringLiteral (completePrompt operation argument)

#2054 removes every directive that existed at its evidence snapshot, but deliberately leaves these three: they were never part of the reproduction, so removing them there would exceed the evidence table. #2060's expected behavior is "no // Stryker disable/enable comments remain in src", so this follow-up is the remaining gap.

Plan

1. Remove the three directives (comment-only change).
2. Re-run the same repro protocol chore(mutation-gate): remove all Stryker directives with evidence-backed exclusions #2054 used (buildManifest + runManifest, extension package) on the refreshed head.
3. Classify every surviving mutant: genuinely equivalent → add a column-pinned entry to scripts/stryker-equivalences.json (file + line + start column + mutator + replacement + rationale); test gap → add a real test.
4. Re-run until blocking = 0 with no stale-entry advisories, then close Mutation gate: remove the 38 legacy Stryker directives on main with evidence-backed central exclusions #2060.

Acceptance criteria

• rg 'Stryker disable' src returns nothing.
• The mutation gate reports blocking = 0 on the cleanup branch and the registry validates against the checked-in source (validateEquivalenceEntries).
• Any newly accepted mutant has a written rationale and a pinned start column.

Split out of #2054 (comment-only directive removal for the 38 pre-existing directives) because these three came from upstream after that PR's evidence snapshot.