[CHORE] Upgrade project baseline to Go 1.25.x

[tazarov]

Context

Dependabot PR #74 (golang.org/x/sys v0.41.0 -> v0.42.0) cannot be merged under the current CI baseline because x/sys@v0.42.0 requires Go 1.25.

Current state:

• go.mod baseline: go 1.24.0
• CI stable baseline: GO_VERSION_STABLE=1.24.x
• Failing message on chore(deps): bump golang.org/x/sys from 0.41.0 to 0.42.0 #74: go.mod requires go >= 1.25.0 (running go 1.24.13; GOTOOLCHAIN=local)

Goal

Adopt Go 1.25.x as the project baseline and keep CI/lint/test/security workflows green across supported OS targets.

Scope

• Update go.mod to Go 1.25.x baseline.
• Update CI matrix and any pinned Go versions to 1.25.x where baseline is expected.
• Ensure GOTOOLCHAIN usage still enforces intended policy (no accidental drift).
• Re-run full CI suite (lint, tests, race subset, integration, vulnerability checks, security scan, build matrix).
• Merge/recreate Dependabot PR chore(deps): bump golang.org/x/sys from 0.41.0 to 0.42.0 #74 after baseline upgrade is validated.

Acceptance Criteria

• main builds and tests pass on updated Go baseline in CI.
• No regression in release workflow/tooling due to Go upgrade.
• Dependabot PR chore(deps): bump golang.org/x/sys from 0.41.0 to 0.42.0 #74 (or equivalent regenerated PR) is mergeable and merged.
• Documentation/README references to Go baseline are updated if present.

Related

• Dependabot PR: chore(deps): bump golang.org/x/sys from 0.41.0 to 0.42.0 #74