Take the direction out of the last cross references

Includes two edits of Anachronaut's: dropping a "See the Assembler Manual"
from text that is now IN the Assembler Manual, and tightening a sentence
about when a vector number has to be agreed.

The first of those was mine to have caught. Moving "Loading A Program From
A Disk" into that manual turned a cross reference into a document telling
you to go and read itself. I checked for dangling references before the
move and found none, because I checked for references by SECTION NAME and
not for references to the manuals themselves.

Checked properly now, both directions: no other document refers to itself,
and nothing that moved says "above" or "below" about something that ended up
in a different file.

The three remaining directional references are gone with them - two that
were correct today and one, "See Numbers You Write Down below", pointing at
a section twenty four lines further down that nothing guaranteed would stay
there. A reference that carries a direction is a reference that goes wrong
the next time anything moves, and this week moved a great deal.

There are none left anywhere in the repository.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW

Programs/CosmOS/README.md

@@ -263,7 +263,7 @@ boundary.
 Applications include `Source/services.asm` to obtain stable names and vector numbers for
 the services CosmOS provides. Neither side ever types a number: the file both of them
 include is the only place any of them is written down. What each service is and what it
-answers in is set out under "What A Program May Ask The System For" below.
+answers in is set out under "What A Program May Ask The System For".
 
 The largest application CosmOS has is the assembler in `Programs/CosmOS/Assembler/`. It
 travels with CosmOS rather than with the emulator, for the same reason the C assembler