[feat] persist thread_dynamic_tools in db

[celia-oai]

Persist thread_dynamic_tools in sqlite and read first from it. Fall back to rollout files if it's not found. Persist dynamic tools to both sqlite and rollout files.

Saw that new sessions get populated to db correctly & old sessions get backfilled correctly at startup:

celia@com-92114 codex-rs % sqlite3 ~/.codex/state.sqlite \      "select thread_id, position,name,description,input_schema from thread_dynamic_tools;"
019c0cad-ec0d-74b2-a787-e8b33a349117|0|geo_lookup|lookup a city|{"properties":{"city":{"type":"string"}},"required":["city"],"type":"object"}
....
019c10ca-aa4b-7620-ae40-c0919fbd7ea7|0|geo_lookup|lookup a city|{"properties":{"city":{"type":"string"}},"required":["city"],"type":"object"}

[jif-oai]

I'm not sure the replace semantic makes sense as we don't want people to replace them after thread start but good for me

[celia-oai]

I'm not sure the replace semantic makes sense as we don't want people to replace them after thread start but good for me

will change the name to persist_dynamic_tools and gate it to only write tools when there's no dynamic tools for a thread