core+gui+cli: anticipation/rebuild dates, preserve relative settings

Fixes around the delivery/build/check date handling (karen7 regtest):

- build_will (GUI + CLI) re-anchors date_to_check to the CURRENT heirs'
  earliest future delivery before building, so an anticipated rebuild is no
  longer blocked by the stale old-will anchor (NO_FUTURE_DATE). The checks of
  the existing will keep their anchored date_to_check.
- _sync_locktime_to_built_txs now PRESERVES RELATIVE locktime/threshold
  recipes ("2y"/"150d") in WILL_SETTINGS instead of freezing them to absolute
  timestamps: the anchored comparisons (resolve_locktime_against_tx and
  resolve_date_to_check with built_locktime) already prevent the daily
  invalidate prompt. Absolute values still sync on a genuine automatic
  anticipation.
- Will.remove_stale_wallet_history drops stale wallet-LOCAL will placeholders
  before every (re)build in GUI and CLI so their coins are available again.
- check_willexecutors_and_heirs raises HeirNotFoundException outside the
  count_heirs gate: a shortened relative recipe on a signed will now triggers
  a plain rebuild ("no heirs" only when there really are none).
- is_locktime_below_threshold compares the settings on one reference frame
  (resolve_guard_threshold), no longer against the built-will anchor.

Tests: purge unit + call-site, no-heirs, guard, anticipated-rebuild
end-to-end (GUI) + CLI mirror + fixed_percent_lists_amount unit,
relative-preserve sync; conftest restores electrum.constants.net after each
test (cross-file pollution guard).

tests/test_core_will.py

@@ -13,8 +13,14 @@ import sys
 
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), os.pardir))
 
+from bal.core.checkalive import resolve_date_to_check
 from bal.core.util import copy_structure
-from bal.core.will import Will, WillItem
+from bal.core.will import (
+    HeirNotFoundException,
+    NoHeirsException,
+    Will,
+    WillItem,
+)
 
 # A valid serialized Bitcoin transaction hex (1 input + 1 P2PKH output, version 2)
 _VALID_TX_HEX = (
@@ -210,6 +216,59 @@ def test_check_heir_added_triggers_rebuild():
     assert raised, "adding an heir must raise HeirNotFoundException"
 
 
+def test_shortened_relative_recipe_on_signed_rebuilds_not_noheirs():
+    """Regression (karen7): heirs shortened "2y"->"1y" on a signed will whose
+    ADVANCED check window is anchored to the frozen built delivery must trigger
+    a plain rebuild (HeirNotFoundException), NOT "No Heirs".
+
+    Earlier the count gate resolved each current relative recipe from *now*
+    while ``check_date`` was anchored to the (longer) frozen built locktime, so
+    every heir fell below the window and was silently excluded -> NoHeirs even
+    though the will simply needs rebuilding on the new, shorter schedule."""
+    lt = 2_100_000_000  # a far-future frozen delivery (a "2y" build)
+    will_heirs = {"alice": ["addr_alice", 5000, "2y"]}
+    current_heirs = {"alice": ["addr_alice", 5000, "1y"]}
+    will = _make_will_with_heirs(will_heirs, lt)
+    will["willid_1"].set_status("COMPLETE", True)
+    check_date = resolve_date_to_check(
+        False, {"locktime": "2y", "threshold": "150d"}, built_locktime=lt
+    )
+    assert check_date < lt  # the anchored window really precedes the delivery
+    raised = None
+    try:
+        Will.check_willexecutors_and_heirs(
+            will, copy_structure(current_heirs), {}, False, check_date, 100
+        )
+    except HeirNotFoundException:
+        raised = "rebuild"
+    except NoHeirsException:
+        raised = "noheirs"
+    assert raised == "rebuild", (
+        f"shortened recipe on a signed will must rebuild, got {raised!r}"
+    )
+
+
+def test_all_heirs_past_check_date_still_noheirs():
+    """The "no valid heirs" gate is preserved: when every heir is coherent with
+    the built will but its delivery lies before ``check_date``, the check still
+    reports NoHeirsException (there is literally nothing future to inherit)."""
+    lt = 1_900_000_000
+    will_heirs = {"alice": ["addr_alice", 5000, str(lt)]}
+    will = _make_will_with_heirs(will_heirs, lt)
+    raised = None
+    try:
+        Will.check_willexecutors_and_heirs(
+            will, copy_structure(will_heirs), {}, False, lt + 86400, 100
+        )
+    except HeirNotFoundException:
+        raised = "rebuild"
+    except NoHeirsException:
+        raised = "noheirs"
+    assert raised == "noheirs", (
+        f"a fully delivered will must report NoHeirs, got {raised!r}"
+    )
+
+
 def test_needs_server_check():
     """Check button selection logic: only a VALID, PUSHED will with a
     will-executor that is not yet CHECKED must be queried on the server.