…ea 5 of #2336

Follow-up to PR #2463 (Areas 1+2+4 of #2336). Completes the directive-handling
portion of the sweep by removing model-state plumbing that was already empty/
trivial after #2335's `createModelSelectionState` removal.

Per the Middleware Boundary Principle: RemoteClaw does NOT control model
selection — CLI runtimes (Claude, Gemini, Codex, OpenCode) own those decisions.
`handleDirectiveOnly` and `applyInlineDirectivesFastLane` carried 10 fields
(`aliasIndex`, `allowedModelKeys`, `allowedModelCatalog`, `resetModelOverride`,
`defaultProvider`, `defaultModel`, `initialModelLabel`, `formatModelSwitchEvent`,
`provider`, `model`) that are now fully dead.

## Changes

- `src/auto-reply/reply/directive-handling.params.ts`: delete all 10 model-state
  fields from `HandleDirectiveOnlyCoreParams`; delete unused `surface?: string`
  from `HandleDirectiveOnlyParams`.
- `src/auto-reply/reply/directive-handling.impl.ts`: queue-validation `channel`
  semantic fix — switch from misused `params.provider` (AI provider, e.g.
  "anthropic") to `params.messageProviderKey ?? ""` (actual message channel,
  e.g. "telegram"). Aligns with `get-reply-run.ts:382` which already passes
  `sessionCtx.Provider` correctly. User-visible effect is limited to
  channel-specific queue config display when running `/queue` without args.
- `src/auto-reply/reply/directive-handling.fast-lane.ts`: drop model-state
  destructures; drop dead `sessionEntry.providerOverride`/`modelOverride`
  reads; simplify return type `{directiveAck?; provider; model}` →
  `{directiveAck?}`. *Note*: `providerOverride`/`modelOverride` ARE written
  by `src/gateway/sessions-patch.ts:213-214` and
  `src/agents/tools/session-status-tool.ts:254-255`, but their downstream
  consumption via this fast-lane path reaches only `isReasoningTagProvider`
  at `get-reply-run.ts:453` (`enforceFinalTag` for google/google-gemini-cli/
  minimax) — vestigial Pi-era plumbing per #2336's gut thesis.
- `src/auto-reply/reply/get-reply-directives-apply.ts`: delete inline empty-
  default `directiveModelState` compat shim (introduced in #2335); delete
  `aliasIndex`/`initialModelLabel`/`formatModelSwitchEvent` threading; inline
  single-call `createDirectiveHandlingBase` factory; drop `provider`/`model`
  from `ApplyDirectiveResult.continue` variant (pure pass-through of inputs
  post-gut).
- `src/auto-reply/reply/get-reply-directives.ts` (required cascade): delete
  dead `initialModelLabel`/`formatModelSwitchEvent` constructions and their
  two param passes (orphaned by the scope reduction in apply.ts); collapse
  `let provider`/`let model` to `const` (no longer reassigned).

## Deferred

- `resolveDefaultModel` stub in `directive-handling.ts` still returns
  `allowedModelKeys`/`allowedModelCatalog`/`resetModelOverride` — never read
  by callers. Separate cleanup wave.
- `aliasIndex` still threaded through `get-reply.ts` → `resolveReplyDirectives`
  (dead throughout). Separate cleanup wave.
- Adjacent Areas 3 (`SessionEntry.thinkingLevel`), 6 (docs), 7 (display audit),
  8 (test-layer hardening) of #2336 remain as separate follow-ups.

## Verification

- `pnpm check`: exit 0 (format + tsgo + oxlint + project-specific lints)
- `pnpm test`: 800 files / 7010 passed / 3 skipped — matches #2463 baseline
- Grep across the 4 target files: zero hits for all 10 gutted symbols

Refs: #2465, #2336, #2335, #2463

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>