Implement native JumpInto animation behavior for grind-out tricks

docs/360-FLIP.md

@@ -85,7 +85,8 @@ lifecycle, not a constant-success condition.
 
 These nonvisual checks cover the ordinary ground route, not every trick in the newly
 connected catalog. Advanced manual/grind-out branches still contain the
-known unsupported `JumpInto` behavior, and the existing separate
+formerly unsupported `JumpInto` behavior (now implemented; see
+[grind-out fix](grind-out-jump-into.md)), and the existing separate
 `AddRunoutAttribs` gap remains. Those handlers were not bypassed. The current
 test does not certify dark catches or the rest of the trick catalog visually.
 

docs/grind-out-jump-into.md

@@ -0,0 +1,23 @@
+# Grind-out JumpInto crash
+
+Observed user-run failure: `logs/game-20260907-213845.stderr.log`, tick528,
+after BS_50_50 entry, reports MotionGraph behavior2228 unsupported JumpInto.
+The preceding run also reached behavior2335 at tick468.
+
+Native reference: TU3 image `default_82000000_011B0000.bin`, base82000000,
+SHA-256 f4aa113eb541bfba03dbc108cf5ab43f58c965b20fa3b82f9c40938a0ad841c4.
+Registration82F88B80 points to factory82BC7A58; the factory reads `attribute`
+and installs vtable8231FBDC. Instance allocation82BB5930 initializes byte8
+true. Begin/End are empty82B61BB8. Update82BACDC0 consumes the byte once,
+queries the authored attribute with mask31, and, if found, seeks playback to
+its begin-time field. Missing markers consume the latch without seeking.
+Static instruction extracts are retained at `logs/biped-<address>.txt`.
+
+The host now parses JumpInto, allocates a per-activation pending flag, and
+performs this query on the live playback tree during Update. It uses the
+existing tree query and absolute set_time paths, including transition and
+blend-tree routing. It does not synthesize a physics impulse or substitute
+the attribute scalar for its timestamp.
+
+Validation: compilation only; user performs gameplay testing. This closes
+the logged unsupported-behavior exit, not a claim of verified retail parity.