Say which memories the model can actually see

Retrieval has been path-scoped since SP3: a memory on a branch this story
never travelled is never sent to the AI. The drawer listed every memory
alike, so on a fork you read "Fell down the cellar stairs; badly hurt" and
reasonably concluded the model knew it. It does not. That is worse than
either hiding the row or retrieving it — it is the screen claiming
something the engine contradicts.

Hiding them is not the answer either; that was the original comment's
point, and it stands. A memory nobody can list is a memory nobody can
delete, in a phase whose rule is that nothing is removed automatically.

So the whole bank still lists, and the rows off the current path are set
back, dashed, and labelled "another branch". MemoryOut.on_path carries it,
computed from the predicate retrieval itself uses rather than a second
spelling of the same idea — two spellings drift, and the failure mode here
is a badge that says the opposite of what the model gets. Pinning does not
override it: the path clause runs before pinning is considered.

The relationship is asymmetric and there is now a test that says so. A fork
borrows its ancestors, so a memory written on the parent is on the fork's
path too; the reverse never is. Worth pinning before somebody makes it
symmetric on the grounds that it looks wrong.

399 tests, three new, egress ceilings intact — the flag costs one id-only
query. Verified in a browser on tools/branch_fixture.py.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015H5qiyiR7gtFQaoDphHZ3g

plan/14-phase-story-tree.md

@@ -767,10 +767,31 @@ never been looked at is whether the *screen* re-reads it. On `tools/branch_fixtu
 switching between the two branches moves the World State drawer from **hp 60 to hp 95**
 live, redraws the bar, swaps the story to the other take (`hp -5`, not `hp -40`) and
 repoints Insights at the other path — "History: 5 of 5 actions", carrying the scratch and
-not the beating. The Memory Bank deliberately does *not* change: the drawer is
-adventure-wide so a memory can always be found and deleted, and it is retrieval that is
-path-scoped (`test_memory_nodes.py`). That split is worth stating out loud, because
-"memories did not change when I switched" reads as a bug and is the design.
+not the beating.
+
+**The memory drawer says which memories the model can actually see.** Retrieval has been
+path-scoped since SP3, so a memory on a branch this story never travelled is never sent.
+The drawer still lists the whole bank — hiding rows would leave memories impossible to
+find and delete, in a phase whose rule is that nothing is removed automatically — but
+listing them *alike* was its own lie: it told the player the model remembers something it
+cannot see. `MemoryOut.on_path` marks them, and the row is set back and labelled *another
+branch*. The flag is computed from **the predicate retrieval itself uses**
+(`path_of(...).clause(Memory, unanchored=True)`), not a second spelling of it, because two
+spellings drift and the failure would be a badge claiming the opposite of what the model
+gets. Pinning does not override it — the path clause runs before pinning is considered.
+
+**The relationship is asymmetric, and a test now says so.** A fork borrows its ancestors,
+so a memory written on the parent is on the fork's path too; the reverse is never true.
+Worth knowing before anyone "fixes" it into a symmetric check.
+
+**One known sharp edge, inherited rather than introduced.** A *hand-written* memory has a
+branch but no depth, and `unanchored=True` keeps it whatever the lineage cap says — so
+one typed on the parent follows you onto a fork whose events it may not describe. That is
+SP3's deliberate choice (`test_a_hand_written_memory_is_not_lost_at_the_first_fork`): the
+alternative is a memory vanishing at the first fork after it was typed. Auto-summarized
+memories carry a depth and *are* capped at the fork, so they behave as expected. If this
+ever bites, the fix is to anchor a hand-written memory at the head depth when it is
+created rather than to change the clause.
 
 **The scroll path was driven, and it holds.** Three prepends on the 602-action fixture,
 60 actions and ~16,200 px each. The same DOM node stayed at viewport top 792 → 787 — a