fix(lease): raise capability-probe timeout to 10s on both halves (#869)

The activation/enforcement capability probes (#869 C1/C4) budget 2.0s for
an out-of-process launch of the mosaic CLI, but the CLI's Node cold start
alone measures 2.2-2.3s on a mid-range workstation (sb-it-1-dt,
2026-08-13). Result: every probe timed out, was treated as NO capability
(fail-closed), and every `mosaic <runtime>` launch on such hosts died
with the misleading version-skew message even though the capability
matched exactly. 10s costs nothing on healthy hosts — the happy path
returns as soon as the probe exits; the timeout only bounds hangs.

Also fixes a latent test-hermeticity bug the new budget exposed:
_resolve_probe_command() ignored the provided environ and resolved
`mosaic` against the ambient os.environ PATH, so the "not resolvable on
PATH" unittest actually spawned the host's real CLI — and only passed on
hosts where that real probe happened to exceed the old 2s timeout.
Resolution now honors the provided environment's PATH (fail-closed when
absent); the unittest suite drops from ~2.1s to ~0.004s, confirming no
real process is spawned.

Verified: version_coupling_unittest.py 15/15; lease-activation-probe
spec 15/15; lease-doctor + mutator-gate specs unchanged vs clean next
(4 acceptance failures pre-exist on 216cd722, unrelated seam); eslint +
prettier clean; tsc --noEmit emits the identical pre-existing error set
as clean next. End-to-end on the affected host: patched gate passes the
real probe in 2.19s and `mosaic yolo claude -p` launches successfully.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Dtdjx4Gxude9fwyLezCrhh

packages/mosaic/framework/tools/lease-broker/activation_version_gate.py

@@ -62,7 +62,14 @@ EXPECTED_ACTIVATION_CAPABILITY: Final[ActivationCapability] = {
 # capability as compact JSON.
 LEASE_CAPABILITY_PROBE_COMMAND: Final = "__lease-capability"
 
-PROBE_TIMEOUT_SECONDS: Final = 2.0
+# Budget for the out-of-process `mosaic __lease-capability` probe. The CLI
+# is a Node program whose cold start alone measures 2.2-2.3s on a mid-range
+# workstation (sb-it-1-dt, 2026-08-13), so a 2s budget made every launch on
+# such hosts fail closed with the #869 skew message even though the
+# capability matched. The timeout only bounds the pathological hang case —
+# the happy path returns as soon as the probe exits — so a generous budget
+# costs nothing on healthy hosts.
+PROBE_TIMEOUT_SECONDS: Final = 10.0
 
 # Override hook: a full shell-style command line (parsed with `shlex.split`)
 # to run INSTEAD of resolving `mosaic` on PATH and appending the probe
@@ -88,7 +95,13 @@ def _resolve_probe_command(environ: Mapping[str, str]) -> list[str] | None:
     if override:
         parsed = shlex.split(override)
         return parsed or None
-    resolved = shutil.which("mosaic")
+    # Resolve against the PROVIDED environment's PATH, not the ambient
+    # os.environ. Before this, a test passing a hermetic environ still
+    # resolved (and spawned) the host's real `mosaic` — masked only on hosts
+    # where the real probe happened to exceed the old 2s timeout. No PATH in
+    # the provided environment means nothing is resolvable (fail-closed),
+    # matching the probe's overall contract.
+    resolved = shutil.which("mosaic", path=environ.get("PATH", ""))
     if resolved is None:
         return None
     return [resolved, LEASE_CAPABILITY_PROBE_COMMAND]