chore: pre pnpm cleanup (#4759)

* chore: drop redundant @types/conventional-commits-parser

conventional-commits-parser v6 ships its own type definitions
(see exports.types in its package.json), so the DefinitelyTyped
@types/conventional-commits-parser package is shadowed and adds
no value. Remove it from the four packages that still list it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: declare @types/node as devDependency where node: APIs are used

Seven packages import from node:* modules (node:module, node:util,
node:readline, node:fs, node:os, node:path, node:url, node:child_process,
node:process) but rely on yarn's hoisting to resolve @types/node.
Declare it explicitly so the dependency is honest and the packages
build under any package manager.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore(prompt): declare rxjs as devDependency

@commitlint/prompt's InputCustomPrompt imports type Subscription
from "rxjs" but does not declare rxjs in its package.json. The
package resolves today only because inquirer transitively pulls it
in and yarn hoists it. Declare it explicitly to make the dependency
honest.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore(cli): declare conventional-commits-parser as devDependency

@commitlint/cli imports type ParserOptions from "conventional-commits-parser"
but does not declare the package. It resolves today only because
@commitlint/types lists it as a runtime dep and yarn hoists it.
Declare it explicitly as a devDependency (type-only import).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: declare vitest-environment-commitlint at root

The root vitest config sets environment: "commitlint", which loads
vitest-environment-commitlint (the workspace package at
@packages/test-environment). Declare it at root so the dependency
is honest and resolves under any package manager, not only via
yarn's workspace hoisting.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: declare commitlint config extends at root

The root commitlint.extends list references @commitlint/config-conventional
and @commitlint/config-workspace-scopes, but neither is declared in the
root devDependencies. They resolve today only because yarn workspaces
hoist them. Declare them explicitly so the root config is self-contained.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>