fix(types,docs): clear the 5 typecheck errors and the fabricated env vars on the base

Third pass over the base-reds, from the 2026-08-06T22:51Z verdict on #9298 —
it reported "Typecheck (core)" with only the FIRST error; there are five, all on
the pure tip 9995bc4893. Two are real production defects.

**Real bugs**

- open-sse/services/compression/engines/ccr/index.ts:295 called
  enforceGlobalBudget(entry.bytes) against an (owner, bytes) signature. The
  `bytes` argument arrived undefined, so `ccrTotalBytes + undefined` is NaN,
  `NaN > MAX` is false (the eviction loop exits immediately) and `NaN <= MAX` is
  false (the re-admit is refused). The #9061 durable tier therefore NEVER
  repopulated its in-memory map: every retrieve after a restart or an eviction
  re-read from SQLite forever, and evictions could not prefer the owning
  principal. Fixed and pinned by a new case in
  tests/unit/ccr-durable-store-9061.test.ts (11/11) — verified failing against
  the buggy call and passing against the fix.
- open-sse/services/combo/fusionPanel.ts:54 read `step.model` after #8894
  widened ComboStep with ComboProviderWildcardStep (which carries modelPattern,
  not model), so a wildcard step in a fusion panel pushed `undefined` onto the
  panel. Now resolved through getComboModelString(), which already handles every
  step shape and returns null for the ones without a concrete model id.

**Type-only**

- accountSemaphore.ts:203 — isBypassed() returns a plain boolean and cannot
  narrow `number | null` (an `x is null | undefined` predicate would be unsound:
  0 bypasses too). Added resolveActiveCap(), the narrowing companion isBypassed
  is now defined in terms of; the acquire path uses the narrowed value.
- comboStructure.ts:140 — same #8894 widening: `prompt` only exists on a model
  step, so it is now read under a kind check.
- firecrawlQuotaFetcher.ts:136 — the function returns full FirecrawlQuota
  objects but was annotated Promise<QuotaInfo | null>, which made the
  custom-base literal an excess-property error. Widened to the accurate type
  (FirecrawlQuota extends QuotaInfo, so callers are unaffected).

**Fabricated docs (the "Docs sync + fabricated-docs (strict)" HARD failure)**

docs/ops/VM_DEPLOYMENT_GUIDE.md recommended OMNIROUTE_MAX_POOL_SIZE and
OMNIROUTE_DB_POOL_SIZE (#9471). Neither is read anywhere in the codebase.
Replaced with the two knobs that do exist and are already documented in
ENVIRONMENT.md: OMNIROUTE_MEMORY_MB and OMNIROUTE_CHAT_MAX_HEAVY_IN_FLIGHT.

typecheck:core 5 errors -> 0. check:fabricated-docs + check:env-doc-sync OK.
accountSemaphore 6/6, ccr-durable-store 11/11, ccr-protocol 9/9,
combo-fusion-strategy 10/10, combo-fusion-comboref 5/5, combo-fusion-warn 4/4,
firecrawl-executor 7/7, executor-firecrawl-fetch 4/4.

Refs #9298

docs/ops/VM_DEPLOYMENT_GUIDE.md

@@ -429,6 +429,7 @@ For deployments on small VPS instances (1 GB RAM or less):
 
 - **Disable background services** — set `OMNIROUTE_DISABLE_BACKGROUND_SERVICES=1` to skip scheduler, MCP server, and periodic maintenance tasks. See `docs/reference/ENVIRONMENT.md`.
 - **Use SQLite WAL mode** — enabled by default, reduces peak memory during concurrent reads.
-- **Limit connection concurrency** — reduce `OMNIROUTE_MAX_POOL_SIZE` and `OMNIROUTE_DB_POOL_SIZE` in your environment.
+- **Cap the V8 heap** — set `OMNIROUTE_MEMORY_MB` (e.g. `512`) so the runtime does not calibrate a ceiling larger than the VM. See `docs/reference/ENVIRONMENT.md`.
+- **Limit concurrent heavy requests** — lower `OMNIROUTE_CHAT_MAX_HEAVY_IN_FLIGHT` (default `1`); excess requests get a retryable `503` with `Retry-After` instead of competing for memory.
 - **Avoid `next build` on the VPS** — build locally and deploy the standalone output (`.next/standalone/`).
 - **Monitor with `top` / `free -m`** — OmniRoute typically uses 200-400 MB RSS at idle on a 1 GB VM.