docs(code-runtime-python): name the roster aliases by subset direction, align metering prose

Rename UnionCoversRoster/RosterCoversUnion to UnionSubsetOfRoster/RosterSubsetOfUnion so
the names read in the same direction as their extends clauses, share the python3 -I -B
flags between the two mirror probes, and align the README and Agent Note prose with the
checkDoneValue JSDoc: the escaped-size scan is the metering itself, not deferred work.
Regenerate docs/module-graph.md, which listed code-runtime-python twice.

packages/code-runtime/code-runtime-python/README.md

@@ -12,7 +12,7 @@ The host and the CPython subprocess exchange a versionless, JSON-lines protocol
 
 - **fd 3, not stdout** — Node pins the channel positionally with `stdio: ['pipe','pipe','pipe','pipe']`; the Python bootstrap reads the same `PROTOCOL_FD` constant. JSON-lines framing.
 - **Host treats every inbound frame as hostile** — model code has full access to fd 3 and can post anything through it, so `validateChildFrame` shape-validates and REBUILDS each frame before the host reads it: forged extra fields never ride along, a non-number call id can never be echoed into a reply, and junk drops to `undefined` rather than throwing in the host's message handler. The Python side trusts host replies (the host is not model-controlled).
-- **Lossless-JSON crossing** — completion values and binding arguments cross as exact JSON. `encodeJsonPlain` serializes a `JSON.parse`-produced value without recursion, so a deep value below the byte budget crosses intact instead of dying on `JSON.stringify`'s stack limit; `checkDoneValue` meters a forged completion value's byte length AND number losslessness in one traversal that rejects an over-budget payload before the incremental work it would add (a non-allocating escaped-size scan, then enqueued children) — the frame's own width is already parsed and capped upstream by the host's fd-3 receive buffer, not re-bounded here; `hasUnsafeIntegerToken` reads the raw frame text to catch an integer token that `JSON.parse` would silently round; `hasNonLosslessNumber` rejects a non-finite or negative-zero number in unbounded `call.args`. Beyond-safe-range integral doubles serialize through `BigInt` digits so the exact integer crosses, not the rounded `String()` form.
+- **Lossless-JSON crossing** — completion values and binding arguments cross as exact JSON. `encodeJsonPlain` serializes a `JSON.parse`-produced value without recursion, so a deep value below the byte budget crosses intact instead of dying on `JSON.stringify`'s stack limit; `checkDoneValue` meters a forged completion value's byte length AND number losslessness in one traversal that rejects an over-budget payload before the incremental work it would add (the enqueued children; strings and keys are metered by a non-allocating escaped-size scan, so the escaped copy is never materialized) — the frame's own width is already parsed and capped upstream by the host's fd-3 receive buffer, not re-bounded here; `hasUnsafeIntegerToken` reads the raw frame text to catch an integer token that `JSON.parse` would silently round; `hasNonLosslessNumber` rejects a non-finite or negative-zero number in unbounded `call.args`. Beyond-safe-range integral doubles serialize through `BigInt` digits so the exact integer crosses, not the rounded `String()` form.
 - **Shared truncation marker** — `logTruncationMarker(maxBytes)` produces byte-identical text on both sides, so a truncated log run reads the same however the cap was hit. The `log` frame's `truncated` flag distinguishes the child ledger's own marker from program output.
 
 ## Model Experience