fix(supervise): remove implicit recursive deadlines

[drewstone]

Outcome

Code-mode programs and live recursive children no longer inherit an elapsed-time cutoff. An omitted or null limit runs until manager cancellation; callers can still declare a positive deadline.

Safety

• Manager cancellation remains authoritative and preserves its reason.
• Explicit deadlines still abort code programs and descendant settlement.
• Invalid code-mode deadlines fail before execution.
• The existing immediate child teardown remains the default unless a caller opts into unlimited settlement.

Proof

• Focused supervision, deadline, graph, and code-mode tests: 190/190.
• Full suite before the child-settlement extension: 3,486 passed, 9 skipped.
• Lint, typecheck, build, generated API references, API surface, and packed-package verification pass.
• Fake-clock checks prove 24 hours does not stop unlimited work and an explicit 25 ms run limit still stops a live child.