Pin golangci-lint to commit c0d3ddc9cf3faa61a4e378e879ece580256d76e5
(v2.12.2) in Dockerfile and script/bootstrap.
Set .golangci.yml to the org-standard v2-schema config already used
across the org's repos (owner-authorized; the same file is being
landed as canonical via a prompts-repo PR). Lint settings live under
linters.settings, so the lll, funlen, cyclop, and dupl thresholds are
actually applied. The informational gomodguard deprecation warning
this config can emit under v2.12 is accepted.
Fix all findings surfaced by the now-active thresholds:
- goconst: shared constants for repeated status, priority, and DNS
fixture strings in watcher.go and the notify, state, and watcher
tests
- dupl: consolidate duplicated ntfy/slack HTTP-error tests and
SendNotification endpoint-error tests behind shared helpers
- lll: wrap long test table entries and comments; shorten one inline
nolint justification
