Facade — taktora-log crate

The thin facade crate that all taktora crates emit through. It owns the LogSink extension trait, the one-shot init builder, and the global log::Log registration — but carries no DLT knowledge (see Shared logging base library (FEAT_0070)).

Feature: taktora-log facade crate FEAT_0071
status: approved
satisfies: FEAT_0070
is satisfied by: FEAT_0073, FEAT_0077, REQ_0800, REQ_0801, REQ_0802, REQ_0803, FEAT_0078
is implemented by: BB_0090

A thin facade crate (taktora-log) that re-exports the log crate’s macros, defines the LogSink extension trait, owns the one-shot process init builder, and registers the global log::Log implementation exactly once per process. The facade carries no DLT knowledge — DLT lives in taktora-log-dlt DLT-protoco... (FEAT_0072). Callers depend only on taktora-log; the backend is configured at process boot.
Requirement: Single facade for all taktora crates REQ_0800
status: implemented
satisfies: FEAT_0071
is verified by: TEST_0800
links outgoing: BB_0090, TEST_0800

Every taktora workspace crate shall emit log records via the log crate facade only. No business crate (executor, connector-*, replay, bounded-alloc) shall depend directly on taktora-log-dlt or any other concrete backend; all calls go through log::info! / log::warn! / log::error! / log::debug! / log::trace!.
Requirement: taktora-log re-exports log macros REQ_0801
status: implemented
satisfies: FEAT_0071
is verified by: TEST_0801
links outgoing: BB_0090, TEST_0801

taktora-log shall re-export the log crate’s macros (info!, warn!, error!, debug!, trace!, plus the structured log::kv surface) so callers that want a single crate dependency can depend on taktora-log alone and use its re-exports as drop-in equivalents of the upstream macros.
Requirement: LogSink trait defines backend extension surface REQ_0802
status: implemented
satisfies: FEAT_0071
is verified by: TEST_0802
links outgoing: BB_0090, TEST_0802

taktora-log shall define a LogSink trait that captures the backend’s responsibilities: emit a log::Record, register an application name (DLT App ID + Context IDs where applicable), accept a runtime log-level change per context, and flush on shutdown. Concrete signatures are locked in during implementation; the trait surface is the only extension point downstream backends target.
Requirement: One-shot init builder selects the backend REQ_0803
status: implemented
satisfies: FEAT_0071
is verified by: TEST_0803
links outgoing: BB_0090, TEST_0803

taktora-log shall expose a builder API that selects the active LogSink implementation at process init and registers it as the global log::Log exactly once. A second init call shall return an error rather than silently override. The builder shall accept any type implementing LogSink; the default value is backend-dependent and resolved by the caller.