Fix CI lint: pin Go 1.25 to match golangci-lint v2.5.0

[Copilot]

Summary

CI lint workflow failing because golangci-lint v2.5.0 (built with Go 1.25) panics when analyzing code with Go 1.26.0.

Why

PR #1993 exposed this: the lint workflow uses go-version: stable which now resolves to 1.26.0, but golangci-lint v2.5.0 binary was compiled with Go 1.25 and cannot parse Go 1.26 source files.

Error:

panic: file requires newer Go version go1.26 (application built with go1.25)

What changed

• .github/workflows/lint.yml: Changed go-version: stable → go-version: '1.25'

Pins CI to Go 1.25.x, matching the Go version used to build golangci-lint v2.5.0.

MCP impact

• No tool or API changes

Security / limits

• No security or limits impact

Tool renaming

• I am not renaming tools as part of this PR

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed

Original prompt

Pull Request: #1993

Fix CI please, lint errors it seems.

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[Copilot]

Pull request overview

Pins the Go version used by the CI lint workflow to avoid golangci-lint panicking when actions/setup-go resolves stable to a newer Go release than the linter binary supports.

Changes:

• Update .github/workflows/lint.yml to use go-version: '1.25' instead of go-version: stable.