…lation)

Channel-side slash commands (/btw, /new, /reboot, /compact, /model, /stop,
/usage, /think, plus the model: interactive-button callback) called the
context-less AgentRouter::resolve, which has no account_id parameter and
only probes the plain channel key. With per-bot defaults stored under
qualified "<channel>:<account_id>" keys (since #2183 / #4861), the lookup
fell through to the system default — collapsing every bot's /command to
the first-registered agent.

/agent <name> stored its override via set_user_default keyed by
platform_id only, with no channel scope, so a /agent in bot-a silently
overrode every other bot's default_agent for that user until daemon
restart (user_defaults is in-memory DashMap, never persisted).

Fix re-keys user_defaults as (Option<channel_account_key>, user_key);
resolve_with_context probes the per-(channel,account) slot first and falls
back to the legacy global slot. handle_command gains an account_id
parameter, builds a BindingContext per call via a resolve_for_command
closure, and writes /agent's selection via the new
set_user_default_for_channel helper. The model: button callback and
resolve_or_fallback's auto-bind path are migrated identically — otherwise
the fallback path would silently re-introduce the leak.

5 regression tests pin the fix:
- router::user_default_does_not_leak_across_bots
- router::channel_scoped_user_default_overrides_global
- router::legacy_set_user_default_is_channel_agnostic
- bridge::command_resolution_respects_account_id (records set_model
  dispatch agent_ids; /model from bot-b then bot-c records
  [agent_b, agent_c] — pre-fix this would be [agent_a, agent_a])
- bridge::agent_command_does_not_leak_across_bots

cargo test -p librefang-channels --lib → 465/465 green.
cargo clippy -p librefang-channels --all-targets -- -D warnings clean.

Closes #5672

…lation) (#5688)

Channel-side slash commands (/btw, /new, /reboot, /compact, /model, /stop,
/usage, /think, plus the model: interactive-button callback) called the
context-less AgentRouter::resolve, which has no account_id parameter and
only probes the plain channel key. With per-bot defaults stored under
qualified "<channel>:<account_id>" keys (since #2183 / #4861), the lookup
fell through to the system default — collapsing every bot's /command to
the first-registered agent.

/agent <name> stored its override via set_user_default keyed by
platform_id only, with no channel scope, so a /agent in bot-a silently
overrode every other bot's default_agent for that user until daemon
restart (user_defaults is in-memory DashMap, never persisted).

Fix re-keys user_defaults as (Option<channel_account_key>, user_key);
resolve_with_context probes the per-(channel,account) slot first and falls
back to the legacy global slot. handle_command gains an account_id
parameter, builds a BindingContext per call via a resolve_for_command
closure, and writes /agent's selection via the new
set_user_default_for_channel helper. The model: button callback and
resolve_or_fallback's auto-bind path are migrated identically — otherwise
the fallback path would silently re-introduce the leak.

5 regression tests pin the fix:
- router::user_default_does_not_leak_across_bots
- router::channel_scoped_user_default_overrides_global
- router::legacy_set_user_default_is_channel_agnostic
- bridge::command_resolution_respects_account_id (records set_model
  dispatch agent_ids; /model from bot-b then bot-c records
  [agent_b, agent_c] — pre-fix this would be [agent_a, agent_a])
- bridge::agent_command_does_not_leak_across_bots

cargo test -p librefang-channels --lib → 465/465 green.
cargo clippy -p librefang-channels --all-targets -- -D warnings clean.

Closes #5672