Fix documentation defects found by an adversarial review

Fifteen findings, all verified before acting. The ones that mattered:

- Corrections added without updating what they corrected. §5's table still
  said a cap-less NURI is one "without :k:", two hundred lines after §4
  established the discriminant is `r:`. Same shape of defect in the P1a
  report, which kept the sentence "it is the owner's keyring, upstream the
  keyring is the wallet" — the exact sentence §4quater declares wrong, and the
  one that produced a global in-memory keyring.

- A wrong source citation: RootCapRefresh/BranchCapRefresh live in
  verifier/src/commits/mod.rs, not repo/src/commit.rs, and are no-op stubs.

- Documentation describing deleted code: isolation.ts, discovery.readIndex,
  the global index, and an acceptance test that was dropped with discovery.

- The P1a implementation report had aged into being wrong in four places
  (caps not persisted, inbox processing not started, plain string types, the
  :k: segment). It is dated, so it now carries a header saying what later lots
  overtook, rather than being rewritten.

- vision.md stated "a document's data is stored encrypted" in the present
  tense. That is the target; here the cap value is the constant OK and nothing
  is encrypted. Said plainly now.

- Prose left mangled by an earlier mechanical find-and-replace, in four places
  I had claimed were repaired.

Also: reach.ts and connect.ts had no home in the permanent docs — the boundary
and the connection sequence are now described in simulation.md, not only in a
brief.

docs/vision.md

@@ -18,7 +18,9 @@ Without a minimum of crypto simulation, damaging shortcuts get taken (reading th
 
 > **A `did` (bare id, WITHOUT a ReadCap) and a NURI (WITH a ReadCap) are treated GENUINELY differently: the former does NOT allow reading the data; the latter is SUFFICIENT and REQUIRED.**
 
-Concretely: a document's data is **stored encrypted** (per-doc symmetric encryption, however lightweight); the **ReadCap = the key**; without it, **decrypting/reading is impossible**. No ACL, no plaintext accessible "on the side". Obtaining read access = **holding the key**, exactly as in the target model.
+Concretely, **in the target**: a document's data is **stored encrypted** (per-doc symmetric encryption, however lightweight); the **ReadCap = the key**; without it, **decrypting/reading is impossible**. No ACL, no plaintext accessible "on the side". Obtaining read access = **holding the key**, exactly as in the target model.
+
+> **Not yet true here, and saying so matters.** The shape is in place — possession decides, every access is confined to the connected virtual user, caps are stored and read back — but the cap value is the constant `OK` and nothing is encrypted. Per-document encryption is **P1b**, and it is one function (`nuri.ts` `mintCap`). Until it lands, nothing this library does may be described as anonymous or private.
 
 ## Shape consequences (to respect everywhere)