refactor: Wave 2 god-file splits — decode/protocol/config/conditions + tdbe::time lift (refs #500)

[userFRM]

What

Wave 2 of the audit-sweep refactor (#500). Five structural changes in one squashed commit:

Split	Old	New	LoC delta
A. decode	crates/thetadatadx/src/decode.rs (2177)	mdds/decode/{error,headers,transport,extract,cell,v3}.rs	structural, public API unchanged
A'. tdbe::time	DST primitives buried in decode.rs	crates/tdbe/src/time.rs	new canonical module reused by mdds/fpss/flatfiles
B. fpss::protocol	fpss/protocol.rs (1613)	fpss/protocol/{contract,wire,subscription}.rs	structural, public API unchanged
C. config	config.rs (1396, 30 flat fields)	config/{mod,mdds,fpss,reconnect,retry,auth,metrics,runtime,env}.rs	nested sub-configs; field-read accessors preserved; field-write callers migrate to nested form
D. conditions	conditions.rs (2749 hand-written tables)	conditions/{mod,tables_generated}.rs + crates/tdbe/data/{trade,quote}_conditions.toml (149 + 75 entries)	TOML-driven codegen via new crates/tdbe/build.rs; round-trip pin test on 12 known entries

Why

Five god-files (over 1300 LoC each) violated the Bloomberg/LSEG-grade engineering bar called out in the 2026-05-06 audit. Splitting them along responsibility lines, lifting cross-crate primitives, and replacing hand-written static tables with TOML-driven codegen brings the codebase in line with institutional norms.

How

• Decode split + tdbe::time lift — Eastern-time / DST math (8 functions) lifted from decode.rs into tdbe::time. Every consumer in crates/thetadatadx/ rewired to import from tdbe::time::*. Public re-exports preserved at thetadatadx::mdds::decode::* so downstream code resolves identically.
• Protocol split — 30+ public symbols + 988 lines of tests redistributed across contract.rs / wire.rs / subscription.rs. Tests follow the symbols they cover. fpss::protocol::* re-exports keep external callers green.
• Config nested — 30 flat fields → 7 nested typed sub-configs. mdds.connect_timeout_secs (default 10s) added — covers the prior LOW finding 3.1. Field-read accessors preserved on DirectConfig for back-compat (config.mdds_host() still works). Field-write callers (78 callsites across crates/thetadatadx/src/{fpss/connection,fpss/mod,macros,mdds/client,observability,unified}, ffi/src/{auth,streaming}, sdks/python/src/lib.rs) migrated to nested form. TOML on-disk shape was already nested; loader rewritten to populate new structs — no migration burden for ~/.thetadatadx/config.toml users.
• Conditions codegen — 149 trade conditions + 75 quote conditions extracted to TOML. crates/tdbe/build.rs reads both files and emits tables_generated.rs with compile-time const arrays. 13 trade descriptions with embedded \" characters use TOML literal triple-strings ('''...'''); zero workarounds needed. New condition_tables_pin test pins 12 known entries (trade 0/30/40/60/61/90/120/148, quote 0/17/50/74) against the live arrays.

Version

Bumps thetadatadx 8.0.35 → 8.0.36 and tdbe 0.12.9 → 0.12.10. Single atomic bump via scripts/bump_version.py 8.0.36. `check_version_sync.py` reports `version sync: ok`.

Test plan

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace — every existing test + new round-trip pin
• cargo deny check
• cargo run -p thetadatadx --bin generate_sdk_surfaces --features config-file -- --check
• cargo check --manifest-path tools/{cli,mcp,server}/Cargo.toml --locked
• cargo clippy --manifest-path tools/mcp/Cargo.toml --all-targets -- -D warnings
• cargo test --manifest-path tools/mcp/Cargo.toml --no-run
• cargo check --manifest-path sdks/{python,typescript}/Cargo.toml --locked
• cargo build -p tdbe --release (build.rs codegen runs at release-build time)
• python3 scripts/check_version_sync.py

Refs #500.