How does satisfies validate shape without widening literal types?

Question presented to candidate: "You have a route map or theme config checked with satisfies. Which literal types survive and which still widen? Walk me through why, and when you would add as const."

What a strong answer should cover:

• satisfies T supplies T as the contextual type; a literal is kept when the contextual type at that position contains literal types of the same kind, and widened otherwise
• So { mode: "dark" } satisfies { mode: "dark" | "light" } keeps "dark", but satisfies { mode: string } or Record<string, unknown> gives string
• Keys are always kept: keyof typeof routes is "home" | "about", while an annotation with Record<string, string> turns keys into string and accepts typos
• satisfies Record<Union, V> makes a map exhaustive: a missing or extra key is a compile error
• as const satisfies T gives validated, deeply readonly literals; the order matters (satisfies T as const is error TS1355); with arrays, check against a readonly array type
• A tuple target such as [number, number] produces a tuple without as const

Clarifying questions expected:

• Should the values be readonly constants, or will they be changed later?
• Do callers need the literal values (for example to derive a union of paths) or only the keys?

Code / implementation expected: Yes — the same object checked against a literal-union target and a string target, with Equal checks proving which literals survive, plus an as const satisfies route map.