feat(journal): QJ1/QJ2 — the journal's pages and their file

The Journal tab is not a quest feature: it is a per-character notebook with no
wire, no server and no dat content. The player writes it, and it persists to a
tagged text file recovered whole from LoadPages/SavePages.

Retail refuses a journal file that does not OPEN with <NEWP>, with its own
message. That strictness is ported rather than softened — accepting such a file
would scatter the first page's text into no page at all. An ABSENT or empty
file is the opposite case and must not error: that is simply a character who
has never written a page.

Three things the format does not say out loud, each with a test:

<PNUM> is written but page order IS file order, so a reader that trusted the
number would reshuffle a hand-edited file. A recorded location of (0, 0) is a
real place, so the location tags are written on a HasLocation flag rather than
on the numbers being non-zero. And the notes box is multi-line while the file
is line-oriented — an embedded newline would read back as a tagless line and
silently truncate the notes, so they are folded to spaces at the write.

The countdown belongs to the page it was started on, and what belongs in the
file is what is LEFT rather than what it started at — saving the start value
would resurrect the full duration on every reload.

Deleting the last remaining page empties the journal instead of leaving a blank
one behind; inventing a replacement would make the journal impossible to empty.
An out-of-range page is refused rather than clamped, because clamping moves the
player somewhere they did not ask to go.

Campaign QJ slices 1 and 2 of 5.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/AcDream.Runtime.Tests/GameRuntimeTests.cs

@@ -244,6 +244,7 @@ public sealed class GameRuntimeTests
             // its three sibling J-owners, before the identity and entity
             // foundations.
             GameRuntimeTeardownStage.ContractsDisposed,
+            GameRuntimeTeardownStage.JournalDisposed,
             GameRuntimeTeardownStage.IdentityDisposed,
             GameRuntimeTeardownStage.EntityObjectsDisposed,
         ];