Fill out the technical index, and let each object answer for its own entry

[gitosaurus]

Takes up More entries for the technical index from the roadmap.

How lookup works now

The entries were a case over main.subj — a dispatch table written by hand,
which is the one thing an object language shouldn't need — and it could only
ever yield text, so an entry had no way to give a conditional hint or to have
any effect at all.

Objects answer 'TechnicalIndexLookup' for themselves now. Whether the library
covers a subject is the subject's own business, and an unhandled message comes
back ABSENT, which is the whole of "not covered": the bicycle repair kit and
the quarter are left out by having nothing written about them anywhere, rather
than by being named in a default branch. Same test the parser already uses on
'look' in gorreven_lex.arch:46.

Sending is also the asking, so an entry has printed itself by the time the
answer arrives. The announcement therefore names the subject and promises
nothing about what follows — true either way, and it shows which object a word
landed on:

> look up quarter
I look up the quarter in the index.
The screen prints NO SUCH ENTRY.  It is, after all, a technical library.

Entries are >> text rather than concatenated string literals, so they read as
prose in the source as well as on the screen.

Verified, not assumed: several types define a default that forwards a
message on rather than letting it fall off the end (hollow_object forwards to
room, large_structure forwards to hollow_object), so "no handler" is not
automatically ABSENT for every type. A sweep of every IsAobject in the game
found exactly one non-ABSENT responder — the object class prototype itself,
which is not a thing a player can name. Also confirmed that a method ending in
an if that doesn't fire returns UNDEFINED and not ABSENT, so a conditional
entry can't print itself and then be denied in the same breath.

The entries

Eighteen added to the five that were there — power, EVA kit, radiation, ship
systems, and a few odds and ends. Several carry a clue the game otherwise
leaves to be found by dying:

• the Geiger counter reads the room and not the wearer, so the coveralls don't
  turn the light green;
• welding light blinds at once rather than by degrees;
• the airlock doesn't check whether anybody is ready before it cycles.

The rest are flavour, which the roadmap explicitly allows: "Most items! They
don't all have to have clues."

Two entries now depend on the state of what they describe, which is the point
of the restructure: the Geiger counter adds a note when it's switched off, and
the calculator stops hinting at its back cover once the back cover is off.

The corrupted message survives, moved to the one place a damaged entry says
something: the captain's ID card.

Also in this PR

• The vending machine prints its terms on its front. The quarter opens the
  calculator and buys the drink, and the machine keeps whatever it's given,
  so spending it first is unrecoverable and nothing said so beforehand. The
  trap stays as designed; what it lacked was the notice any machine of this
  kind would have printed on it. (This rode along in c5355b1, whose message
  doesn't mention it.)
• The cartridges are an object. They were the first noun in the room
  description and the only one that couldn't be looked at.
• never_read was never cleared, so the index introduced itself as if for
  the first time however often it was read.
• Three typos in text the player sees: "the walls are lines with", "artifical",
  "physican".

Testing

--test: 18 suites, 0 failures. Every entry verified reachable by the name a
player would type, from a scratch harness that starts in the library, including
both branches of each conditional entry.