Add internal/planrender adapter for query plan rendering

[apstndb]

Summary

• Library-only slice: new internal/planrender adapter renders Spanner query plans as text, DOT, Mermaid, D2, SVG, or PNG from a rows-less ResultSet envelope (metadata.rowType + stats).
• No CLI flags and no main.go behavior change. --plan-format=text|dot|mermaid|d2|svg|png wiring waits for the split-output feature.
• Adds github.com/apstndb/spannerplan v0.3.0 and github.com/apstndb/spannerplanviz v0.11.0. No nographviz build tag in this PR.

API

Package internal/planrender (v0/experimental libraries stay behind this boundary; only spannerpb types leak):

• type Format string with FormatText, FormatDOT, FormatMermaid, FormatD2, FormatSVG, FormatPNG
• ParseFormat(string) (Format, error)
• Format.IsBinary() bool (true for PNG)
• Format.NeedsGraphviz() bool (true for SVG/PNG)
• type Options struct { TextStyle, WrapWidth, PrintSections, Full, ShowQuery, ShowQueryStats, Query }
  • Text defaults: TextStyle=current, WrapWidth=0, PrintSections=basic
  • Graph defaults: StructureBuildOptions; Full selects FullBuildOptions
  • Options that do not apply to the chosen format are rejected (not ignored)
• Render(ctx, w, format, rowType, stats, opts) error
  • Text: reference.RenderTreeTableWithOptions(..., RenderModeAuto, ...)
  • Graphs: visualize.BuildPlan(rowType, stats, buildOpts) then dot/mermaid/d2 renderers, or graphviz.NewRenderer(...).Render for SVG/PNG
  • Typed protobufs only (no ExtractQueryPlan JSON round trip); rowType may be nil
  • Missing/empty plan: ErrNoQueryPlan (--query-mode=PLAN, PROFILE, or WITH_PLAN_AND_STATS)
  • Traversal-budget and cycle errors from spannerplan are surfaced
  • Graphviz runtime is created and closed inside spannerplanviz v0.11.0 Renderer.Render

Dependencies

Module	Version	Why
github.com/apstndb/spannerplan	v0.3.0	Text table renderer; occurrence-aware parent links; traversal budgets/cycle detection
github.com/apstndb/spannerplanviz	v0.11.0	Graph builders/renderers; requires Go 1.25 and spannerplan v0.3.0; fixes Apply-with-repeated-child edge labels

v0.11.0 is the published tag (local checkout was v0.10.2). Indirectly pulls goccy/go-graphviz v0.2.10 and tetratelabs/wazero v1.10.1 (pure Go, CGO_ENABLED=0). golang.org/x/text moves v0.37.0 → v0.38.0 via golang.org/x/image.

Measurements

Scratch CLI builds that keep planrender.Render live (not committed). Baseline is origin/main 5dbad3b in .tmp/baseline-main.

Binary	Bytes	MiB	Delta vs base
origin/main CLI	53,463,906	51.0	—
CLI + planrender without Graphviz (dot/mermaid/d2/text)	53,590,658	51.1	+126,752 (124 KiB)
CLI + full planrender (SVG/PNG / wazero)	59,873,906	57.1	+6,410,000 (6.11 MiB)

• spannerplan + spannerplanviz without Graphviz: +124 KiB
• extra Graphviz/wazero runtime: +6.00 MiB
• Under the design note's ~10 MiB skip-the-tag heuristic. Maintainer can still add nographviz later.

Cross-compile (CGO_ENABLED=0 go build ./internal/planrender/... and go vet)

Target	build	vet
linux/amd64	OK	OK
linux/386	OK	OK
linux/arm64	OK	OK
windows/amd64	OK	OK
windows/386	OK	OK
windows/arm64	OK	OK
darwin/amd64	OK	OK
darwin/arm64	OK	OK

linux/386 and windows/386 build; wazero has no optimizing compiler on 386 (interpreter fallback). Not benchmarked here.

govulncheck

govulncheck ./... exit 1 (findings). Same two call-site vulns on origin/main:

ID	Module	Branch	origin/main	Notes
GO-2026-6061	google.golang.org/grpc@v1.81.1 (fixed v1.82.1)	yes	yes	Pre-existing; traces through main.go / internal/grpctest
GO-2026-5970	golang.org/x/text (fixed v0.39.0)	v0.38.0	v0.37.0	Pre-existing (< v0.39.0); this PR only moved 0.37.0 → 0.38.0

No new vulnerability IDs. Not upgraded here (out of library-adapter scope).

Tests

Command	Exit
go build ./...	0
go vet ./...	0
go test ./internal/planrender ./params/... ./jqresult/... ./resultset/...	0
GOTOOLCHAIN=go1.25.13 golangci-lint run	0
golangci-lint run (host go1.27.1)	1 (toolchain typecheck on samber/lo / math/rand/v2; reran with Go 1.25.13)
govulncheck ./...	1 (findings above)
DOCKER_HOST=unix://$HOME/.colima/default/docker.sock TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE=/var/run/docker.sock go test ./...	0

planrender coverage: PROFILE and PLAN-style AUTO text goldens (testdata/profile/singers_limit3.json); DOT/Mermaid/D2 smoke (root operator); one SVG (<svg) and one PNG (magic bytes) on a 1-node plan, skippable with -short; nil/empty plan, dangling childIndex, DAG repeated child, cycle, Unicode/control predicates, option validation matrix, cancelled graph context.

Follow-up

CLI wiring after split-output lands: --plan-format=text\|dot\|mermaid\|d2\|svg\|png and the text/graph tuning flags from docs/design/plan-rendering.md, dispatching json/yaml locally and everything else to planrender.Render.