docs: document the +cric cryptosuite that replaced +crub in Ames and Jael

[sigilante]

Sixth PR from the audit against urbit/urbit@08026c84b2. Cross-cutting — this one was flagged independently by two passes of the audit, in two different doc trees, which is what pushed it up the queue.

Companion PRs: #266, #267, #268, #269, #270.

What changed upstream

+cric:crypto (zuse.hoon:1489) is the suite Ames and Jael now use. Unlike +crub, which is fixed to Suite B, +cric is a door over a tagged payload and can carry either suite:

$%  [suite=%b pub=[cry=@ sgn=@ ~] sek=...]
    [suite=%c pub=[cry=@ sgn=@ tw=[ugn=@ dat=@ xtr=@]] sek=...]
==

Counted rather than assumed: sys/vane/ames.hoon contains zero references to crub and 26 to cric. Jael builds keys through +cric too (pit:nu:cric:crypto, nol:nu:cric:crypto — jael.hoon:266,338,854,1260,1271,1306).

+crub still exists in zuse (:1703) and its documentation is kept — it's now labelled superseded rather than deleted, since the docs previously called it "the only cryptosuite which Ames makes use of".

One structural change worth calling out: the symmetric arms moved into a +cyf sub-core. What the docs called +en:crub:crypto is now +en:cyf:cric:crypto. All four sub-cores are documented: as, ex, nu, cyf.

Corrections that required reading the current state, not the migration code

Two things here are worth a reviewer's attention, because the obvious search gives the wrong answer.

1. Ames no longer stores a crypto core at all. The audit described Ames as wrapping _cric:crypto in an internal +acru-25 core with a legacy +acru-12 for old peers. That is true of the migration types only. The current +$ axle (lull.hoon:1601, axle-31) has no crypto-core field — it stores [saf=keypairs =ring =pass], where +$ keypairs is [pub=public-keys sek=private-keys] (lull.hoon:1069). +acru-12 (ames.hoon:817) and +acru-25 (:881) appear only inside versioned definitions like ames-state-13 and ames-state-22.

The docs now state this explicitly, so the next reader doesn't repeat the mistake. (This is the same shape of trap as the heeds field in #269.)

2. Comet self-attestation no longer signs via an acru core. +etch-open-packet (ames.hoon:423-438) signs with (sign-raw:ed:crypto - [sgn.pub sgn.sek]:saf). The documented +sign:as:crub was wrong in both suite and arm.

Not changed, having been checked

• jael/data-types.md $point and $key-update already carry crypto-suite=@ud and match lull.hoon:4323,4327. The audit listed these as needing the field added — they did not. Only $point's prose omitted an explanation of what crypto-suite means, which is now supplied.
• +crub:so (stdlib/4l.md) is an unrelated date-parsing arm in +so. Untouched.
• core-academy/ca02.md quotes +crub source, but Core Academy declares itself a snapshot at Zuse 412k.

All anchor links in the touched files were verified to resolve, and this branch was test-merged against the five open companion PRs — all clean.

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