fix(core): chant build --components --generate --format json forwards env (#2060)

[lex00]

Closes #2060.

#2046 put env on the components generator result so a structured consumer can tell which environment a generated pipeline deploys. The JSON printer in the build handler never forwarded it: chant build --components --generate --format json emitted only stages, jobs and yaml, so the consumer had to re-parse the YAML to recover the environment. The graph --components --format ir projection path already forwarded env; this makes the build handler match it.

env is spread into the JSON result when the generator returns one and omitted otherwise, so existing consumers of the three-key shape see nothing new unless the generator has an environment to report. Text output is unchanged.

Tests in build.test.ts: env present in JSON output, env omitted when the generator returns none, text format prints only the raw YAML. The build reference page's description of the JSON shape now lists env.

Gates

Run by the orchestrator in the worktree after the agent's own run.

npx vitest run packages/core           385 files, 6160 passed
npx tsc --noEmit                       clean
npx tsx scripts/typecheck.ts           37 known failure(s), no regressions (37 baselined)
node scripts/lint-docs-sentences.mjs   4111 gated finding(s), no regressions (4111 baselined)
node scripts/check-docs-diataxis.mjs   clean

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