feat(init): add generic editJson + deferred note primitives

[Adi-ty]

What this PR does

Extends wp-tooling's feature kernel with the editing and reporting primitives wp-devtools needs, effort: a generic journaled editJson for managing both halves of a feature's state, a deferred "next steps" channel consumed by the dev-tools init feature, and a corrected npm install hint.

Part of

• Part of rtcamp/wp-devtools#48
• Part of rtcamp/wp-devtools#49

Changes

• Generalise editPackageJson into api.editJson(rel, mutator, opts) — preserves indentation, optional create + indentFrom for absent files, and a parse error that names the offending file; editPackageJson is now a thin wrapper. Fully journaled: rollback restores an existing file or removes a created one.
• Add api.note(message) — defers "do this next" lines past the spinner; toggleFeatures flushes them once under a Next steps heading after transitions, draining the queue so a manage-mode toggle loop never reprints. Notes roll back with the journal when a hook throws.
• Narrow touchesPackage to dep changes only — a scripts-only feature no longer prompts npm install.
• Ship tests/init/features.test.js (22 tests) covering editJson indent/create/rollback, note queueing/flush/rollback, the npm-install hint, and a full enable/disable/detect round trip against a committed-manifest + gitignored-local-override composite.

How I verified

$ npm run lint
(clean — zero errors)
$ npm test
Test Suites: 53 passed, 53 total
Tests:       749 passed, 749 total

Acceptance criteria

Runtime behavior

• CPI-enablet + local override can be written idempotently, detected, and removed cleanly on disable
• Notes print once, after transitions, and never on a failed hook
• Scripts-only features stay quiet about npm install
• Existing non-TTY / CI behaviour unchanged (full suite green)

Code quality

• Lint — zero errors
• Static analysis — zero errors
• Tests pass (749/749)