CraftReplDev: CRAFT-mode replication device foundation

[sbinmalek]

Summary

Implements the S1 foundation for CRAFT-mode replication.
Introduces CraftReplDev as a parallel to HomeStore's ReplDisk — CRAFT-mode
volumes will own one of these instead of the solo repl_dev. Non-CRAFT volumes
are completely unaffected.

Changes

• home_blocks.hpp: Add replication_mode enum (DISABLED / CRAFT) and a
  repl_mode field to volume_info (defaults to SOLO; all existing callers
  compile unchanged).

• src/lib/craft/CMakeLists.txt: New homeblocks_craft OBJECT library;
  wired into src/lib/ via add_subdirectory and linked into the final
  homeblocks library.

• craft_repl_dev.hpp: All CRAFT wire types (CraftPartitionState,
  LSNPair, LoginResult, JournalSlot, replica_endpoint), the
  CraftJournalBackend abstract interface (enables mock injection for unit
  tests per AC), and the full CraftReplDev class declaration including the
  nested CraftRaftListener.

• craft_repl_dev.cpp: Constructor, real get_lsns() / get_rs_commit_lsn()
  implementations, and stubs (returning ENOTSUP) for all remaining methods
  pending S2–S7.

What is NOT in this PR

All method bodies except get_lsns / get_rs_commit_lsn are stubs. Subsequent
stories fill them in: S2 (write), S3 (commit/read), S4 (truncate), S5 (RAFT
entries), S6 (peer data exchange), S7 (login orchestration).

Test plan

• conan create . -c tools.build:skip_test=True builds cleanly with the new
  OBJECT library linked in
• Existing volume tests pass unchanged (non-CRAFT path untouched)
• Unit tests for CraftReplDev will be added in S2 (src/tests/craft/)
  once the write path exists

🤖 Generated with Claude Code

[szmyd]

There is no RAFT in solo ReplDev; just the data journal. Maybe we just call this "DISABLED" or "NONE"?

[sbinmalek]

Will change it to Disabled

[szmyd]

This looks good! It's at least a starting point if not 100% correct; but gives us something to "speak to" when we have our CRAFT discussions. 👍

[szmyd]

lgtm

[Copilot]

Pull request overview

Implements the initial scaffolding for CRAFT-mode replication by introducing a new CraftReplDev abstraction (parallel to HomeStore’s ReplDisk) and wiring a new homeblocks_craft OBJECT library into the build so CRAFT components can be compiled/linked without affecting existing (SOLO) volumes.

Changes:

• Added replication_mode (SOLO / CRAFT) and repl_mode to volume_info (defaulting to SOLO) in the public API.
• Added new src/lib/craft/ module containing CRAFT wire types, a journal backend interface for testability, and a CraftReplDev class with initial implementations for get_lsns() / get_rs_commit_lsn() plus stubs for future stories.
• Integrated the new craft OBJECT library into src/lib and linked its object files into the final homeblocks library target.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lib/volume/CMakeLists.txt	Links the new craft OBJECT library objects into the main library build.
src/lib/craft/craft_repl_dev.hpp	Introduces CRAFT wire types, CraftJournalBackend, and the CraftReplDev interface + RAFT listener declaration.
src/lib/craft/craft_repl_dev.cpp	Implements constructor and LSN snapshot methods; adds ENOTSUP stubs for remaining methods.
src/lib/craft/CMakeLists.txt	Defines the new ${PROJECT_NAME}_craft OBJECT library.
src/lib/CMakeLists.txt	Adds the craft/ subdirectory to the build.
src/include/homeblks/home_blocks.hpp	Adds replication_mode and a repl_mode field to volume_info, including updated move-ctor and to_string().

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