feat(storage): export portable ledger archives

[kaikisegfault]

Advances #11.

Implements the ADR 0007 PSAR v1 engine-independent archive codec and a serialized SQLite export captured from one fully verified read transaction. Export exact-projects canonical genesis, ordered block/journal rows, and a fresh head snapshot, then semantically replays the archive before returning bytes.

Verification:

• focused GCC debug build with -Wall -Wextra -Wpedantic -Werror
• 4/4 focused storage tests pass: ledger, history, snapshot, archive
• frozen 3,745-byte populated-block archive fixture and digest
• zero-block, empty-block, populated-block, hostile framing/count/length, corruption, truncation, trailing-byte, deterministic multi-block export, retained-snapshot, and reopen coverage
• Clang sanitizer CMake configure passes and exposes the fifth bounded archive libFuzzer target
• git diff --check, shell syntax, and Python bytecode compilation pass

The GitHub compiler/sanitizer matrix on this exact commit is the completion gate.

[kaikisegfault]

Completion evidence for exact candidate 0321d956d01d634333e62bb04232be78e0322abc:

• Actions run 30165268802 passed all four jobs.
• GCC debug: 18/18 tests.
• GCC ASan/UBSan: 18/18 tests.
• Clang debug: 18/18 tests.
• Clang ASan/UBSan: 23/23 tests, including all five bounded fuzz smoke targets and the new archive decoder fuzzer.
• Focused local GCC storage gate: 4/4 tests.

The diff and documentation were self-reviewed; git diff --check, shell syntax, Python bytecode compilation, and Clang sanitizer configuration passed.