Preserve logs on thrown executor paths, charge every call attempt, and render 2020-12 keywords honestly

[zackbart]

Closes #543 (items 1, 3, 4, 5; items 2 and 6 landed in #546 and #545).

• Logs survive every failure. QuickJS streams accepted console entries to the parent within the IPC bound, so a program that is cancelled, killed at the deadline, crashed, or lost to an IPC failure still returns what it printed (4,000-character cap). A normal reply keeps its complete log array; the two copies are never joined.
• Accounting. Every connecta.call attempt spends one host call on entry, so unknown addresses and other pre-dispatch refusals cannot loop for free. The request-held failure list used to re-type escaped errors keeps the most recent 64. An empty terminal error string is a failure with a fixed message on both the parent and the child transport.
• Rendering. prefixItems renders as a tuple, dependentSchemas and if/then/else shapes are marked /* conditional */ with the truncation flag, and $dynamicRef resolves like $ref (else unknown, flagged).
• Pool timing oracle is accepted and documented in auth.md: pool names grant no access, a fixed delay cannot hide unbounded grant I/O, and probing grants for unknown names would add work while holding a permit.

Full npm run check passes on this branch (pre-rebase; CI is the check of record for the rebased tree).

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