Further root readme bump, factor `.clearing` content

In line with our move to `uv` and recent `nix` support update a bunch of
the summary content and factor out the order-control section to a new
`.piker.clearing` readme file with embedded todos therein.

README.rst

@@ -121,34 +121,34 @@ various sub-readmes:
 
 spawn a daemon standalone
 *************************
-we call the root actor-process the `pikerd`. it can be (and is
-recommended normally to be) started separately from the `piker chart`
-program::
+we call the root actor-process the ``pikerd``. it can be (and is
+recommended normally to be) started separately from the ``piker
+chart`` program::
 
     pikerd -l info --pdb
 
-the daemon does nothing until a `piker`-client (like `piker chart`) connects
+the daemon does nothing until a ``pikers`-client (like `piker chart`) connects
 and requests some particular sub-system. for a chart connection
-`pikerd` will spawn and manage at least,
+``pikerd`` will spawn and manage at least,
 
-- a data-feed daemon: `datad` which does all the work of comms with
-  the backend provider (in this case the `binance` cex).
-- a paper-trading engine instance, `paperboi.binance`, (if no live
+- a data-feed daemon: ``datad`` which does all the work of comms with
+  the backend provider (in this case the ``binance`` cex).
+- a paper-trading engine instance, ``paperboi.binance``, (if no live
   account has been configured) which allows for auto/manual order
   control against the live quote stream.
 
 *using* an actor-service (aka micro-daemon) manager which dynamically
-supervises various sub-subsystems-as-services throughout the `piker`
+supervises various sub-subsystems-as-services throughout the ``piker``
 runtime-stack.
 
 now you can (implicitly) connect your chart::
 
     piker chart btcusdt.spot.binance
 
-since `pikerd` was started separately you can now enjoy a persistent
+since ``pikerd`` was started separately you can now enjoy a persistent
 real-time data stream tied to the daemon-tree's lifetime. i.e. the next
 time you spawn a chart it will obviously not only load much faster
-(since the underlying `datad.binance` is left running with its
+(since the underlying ``datad.binance`` is left running with its
 in-memory IPC data structures) but also the data-feed and any order
 mgmt states should be persistent until you finally cancel ``pikerd``.