Remediate all lint findings under the canonical golangci-lint config

Fix every finding surfaced by the canonical .golangci.yml with
golangci-lint v2.12.2 (refs #61), behavior-preserving throughout:

- err113: dynamic errors replaced with package-level sentinels and %w
  wrapping; direct comparisons converted to errors.Is
- goprintffuncname: printf-style helpers renamed with an f suffix
  (ui.Writer message methods, cli.ReportErrorf, database.Fatalf,
  vaultik stdoutf) and all call sites updated
- revive: stuttering type names renamed (blob.Handler, blob.WithReader,
  blob.ChunkPosition, storage.URL, storage.Info), doc comments added,
  unused parameters blanked, package comments added
- contextcheck/noctx: ctx threaded through blob.Packer
  (AddChunk/Flush/FinalizeBlob/PackChunks) and scanner call sites;
  context-aware exec and sql variants used
- funlen/cyclop/gocognit/nestif/dupl: oversized or duplicated
  functions split into focused helpers across production and test code
- paralleltest/tparallel/thelper/usetesting/testpackage: tests
  parallelized where safe (global log.Initialize kept in the serial
  phase), helpers marked, t.TempDir adopted, external test packages
  where only exported API is used
- gosec: integer conversions clamped or justified, header timeouts
  added, remaining findings suppressed with per-site justifications
- mnd/goconst/lll/wsl_v5/nlreturn/noinlineerr/errcheck and other
  mechanical findings fixed directly

Remove the deprecated log.LogOptions alias (callers migrated to
log.Options). make check is green.

TODO.md

@@ -14,13 +14,16 @@ pre-1.0
 
 # Next Step
 
-Remediate the 2,990 lint findings surfaced by the standard
-`.golangci.yml` (issue #61): behavior-preserving fixes in per-linter or
-per-package chunks, mechanical linters first, until `make check` is
-green on `main`.
+Reconcile the uncommitted ARCHITECTURE.md edits on main: finish and
+commit, or revert.
 
 # Completed Steps
 
+- 2026-08-07: Updated golangci-lint to v2.12.2 everywhere it is pinned
+  (`Dockerfile` lint stage, `Makefile` deps target), replaced
+  `.golangci.yml` with the canonical config (v2 schema, `default: all`),
+  and remediated all lint findings it surfaced (issue #61):
+  behavior-preserving fixes across every package, `make check` green.
 - 2026-08-07: Added the standard `.golangci.yml` and `.editorconfig`
   (issue #59); lint findings under the new config are tracked in issue
   #61. `script/bootstrap` now installs sqlite3 (needed by tests).
@@ -46,8 +49,6 @@ green on `main`.
 
 # Future Steps
 
-- Reconcile the uncommitted ARCHITECTURE.md edits on main: finish and
-  commit, or revert.
 - Review stale local branches (add-godoc-to-cli-package,
   feature/pluggable-storage-backend) and merge or delete them.
 - Define remaining scope for a first tagged release and cut v0.1.0.