Recent changes seem to have broken the lint step in CI:

```
❯ mise run lint
[lint:shellcheck] $ ~/entire/cli/.worktrees/fix-lint-on-main/mise-tasks/lint/shellcheck
[lint:go] $ ~/entire/cli/.worktrees/fix-lint-on-main/mise-tasks/lint/go
[lint:gomod] $ ~/entire/cli/.worktrees/fix-lint-on-main/mise-tasks/lint/gomod
[lint:mise] $ ~/entire/cli/.worktrees/fix-lint-on-main/mise-tasks/lint/mise
[lint:gofmt] $ ~/entire/cli/.worktrees/fix-lint-on-main/mise-tasks/lint/gofmt
[lint:mise] Finished in 298.9ms
[lint:gofmt] Finished in 727.6ms
[lint:shellcheck] Finished in 736.5ms
[lint:go] golangci-lint has version 2.11.3 built with go1.26.1 from 6008b81b on 2026-03-10T10:25:44Z
[lint:gomod] Finished in 1.10s
[lint:go] cmd/entire/cli/review_context.go:383:10: string `checkpoint` has 3 occurrences, make it a constant (goconst)
[lint:go] return "checkpoint"
[lint:go] ^
[lint:go] cmd/entire/cli/runner_gather.go:57:8: string `trail` has 3 occurrences, make it a constant (goconst)
[lint:go] case "trail", "trails":
[lint:go] ^
[lint:go] 2 issues:
[lint:go] * goconst: 2
Finished in 21.36s
[lint:go] ERROR task failed
```

We should address that.

---

`goconst` isn't firing in scratch — likely no `go.mod` so analysis is skipped. Let me add a module.

---

`mise run lint` → **0 issues** (cold cache, matching a fresh CI run). Fixed.

## What I changed

Two `goconst` findings — repeated string literals `checkpoint` and `trail` crossing the 3-occurrence threshold after the recent `trail tune` refactor added a new occurrence of each in `runner_gather.go`:

- **`review_context.go`** — `reviewContextCheckpointNoun` was hand-rolling singular/plural, duplicating the existing `pluralize` helper. Replaced its body with `pluralize("checkpoint", count)`. Bonus: removes a duplicated helper, and the string is now a call argument (which goconst ignores).
- **`runner_gather.go`** — named the two flagged source tokens as `sourceCheckpoint` / `sourceTrail` constants and referenced them in the parse switch (plural aliases stay as literals since they're under threshold).

The unrelated `writestring`/`stringsseq` IDE diagnostics are from a different linter set (not in this repo's `.golangci.yaml`) and are pre-existing — `mise run lint` passes clean.

One note on why this looked confusing: those strings actually occur ~25/14 times package-wide (mostly tests), all baseline-suppressed by golangci-lint-action's new-issue filtering. The refactor added a _new_ occurrence in a new file, which is what tripped CI. These two edits neutralize the new occurrences, so lint is green again without touching the grandfathered ones.

Want me to commit this?

---

Could you assign trails and checkpoints to constants as well for consistency?

---

All four source tokens are now constants and the switch reads consistently:

```go
const (
	sourceCheckpoint  = "checkpoint"
	sourceCheckpoints = "checkpoints"
	sourceTrail       = "trail"
	sourceTrails      = "trails"
)
```

```go
case sourceCheckpoint, sourceCheckpoints:
	s.checkpoints = true
case sourceTrail, sourceTrails:
	s.trails = true
```

Lint stays clean (0 issues). Want me to commit?

---

Committed. Now running the PR skill.

### Commit message

`77cada3fix(lint): resolve goconst findings for checkpoint/trail`

Recent refactors pushed the repeated "checkpoint" and "trail" string literals over goconst's occurrence threshold, breaking CI lint.

Reuse the existing pluralize helper in `reviewContextCheckpointNoun` (which also drops a duplicated helper), and name the tune-source tokens as constants in `parseTuneSources`.

---

Draft PR created: [https://github.com/entireio/cli/pull/1594](https://github.com/entireio/cli/pull/1594)