Cardano Updates

* make-install-plan: Include info needed for backpack.

* Support backpack builds.

Fixes #244

* fixup! Support backpack builds.

* Bump head.hackage

* Dump head.hackage

* Work around GHC JS backend not producing .o files for backpack signatures

GHC's JavaScript backend doesn't produce .o files for backpack signature
module instantiations, causing ar to fail when creating library archives.

Fix this by replacing the ar command in GHC's settings with a wrapper
that filters out missing .o files from both command-line arguments and
response files. The fix only applies to GHCJS instantiated backpack
builds, leaving all other builds unchanged.

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Co-authored-by: Hamish Mackenzie <[email protected]>

Inbound connections are clients pulling data from us. They should not
participate in chain selection — letting them publish PeerTipUpdateEvents
causes spurious chain switches when ephemeral inbound peers report a tip
and then disconnect.

Add IsInboundConnection to ConnectionManager and use it to gate
PeerTipUpdateEvent publication in chainsyncClientRollForward.

Also fix a blockfetch pipeline gap caused by the global seenHeaders dedup:
when an inactive outbound peer consumes isNew=true for a header before the
active connection's callback runs, the active peer later sees isNew=false
and the ChainsyncEvent is silently dropped — blockfetch never fires. Detect
this case (isNew=false on the active connection) and publish the event
anyway so the ledger can queue the block for fetch.