fix(deps): migrate to lipgloss v2 (charm.land/lipgloss/v2)

[ryanlewis]

What

Migrates things-cli from lipgloss v1 → v2, replacing the unmergeable renovate PR #73.

Why #73 can't work (two independent reasons)

1. The module was renamed. lipgloss v2's go.mod declares module charm.land/lipgloss/v2. Renovate just appended /v2 to the old github.com/charmbracelet/lipgloss path — which Go rejects outright (declared-path mismatch). The import must become charm.land/lipgloss/v2.
2. go.sum was never populated (renovate's artifacts step failed), and renovate doesn't touch the breaking API changes.

The real change

v2 removes the global renderer: lipgloss.SetColorProfile/ColorProfile are gone and Style.Render() now always emits full-fidelity ANSI. Downsampling/stripping moved to write time via colorprofile.Writer{Forward, Profile}. So the --color mechanism moved from render-time to write-time:

• internal/output/style.go — package colorProfile var + detectProfile()/newWriter() helpers; SetColorMode maps auto→colorprofile.Detect, always→TrueColor, never→NoTTY.
• internal/output/output.go — Print/PrintTaskWithChecklist wrap the caller's writer with newWriter() for styled (non-JSON) paths only.
• internal/output/style_test.go — tests assert at the writer boundary (v2 helpers always emit ANSI); hermetic TestMain no-color baseline; new auto/non-TTY coverage.
• go.mod/go.sum — charm.land/lipgloss/v2 v2.0.3; colorprofile promoted to direct; github.com/muesli/termenv dropped entirely.

Behavior parity (verified end-to-end on the real binary)

--color	piped (non-TTY)
auto	strips ANSI (exactly like v1)
always	forces color even when piped
never	fully plain

Verification

• go build ./... ✅ · go vet ./... ✅ · golangci-lint run ./... clean ✅
• go test -race ./... → 240 pass ✅ · go mod tidy no-op ✅ · go mod verify ✅
• Two rounds of adversarial multi-agent review (migration lenses + 9-angle /code-review); no correctness bugs in the migration. Fixes applied: hardened the new auto test against TTY_FORCE, strengthened the always test to assert color (not just decoration), de-duplicated the profile-detection expression.

Notes

• No subcommand surface change — internal/skill/SKILL.md and docs unaffected; Kong still enforces the auto|always|never enum.
• Supersedes fix(deps): update module github.com/charmbracelet/lipgloss to v2 #73.