routes-file-hono: add TPH subtype gating (pre-existing gap)

[dmealing]

Follow-up from #248 (PR #249), design spec §9e.

The Hono routes generator (codegen-ts/src/generators/routes-file-hono.ts) lacks the !isTphSubtype(e) exclusion that the Fastify routes-file.ts has, so a TPH (single-table discriminator) subtype gets a standalone Hono routes file it shouldn't (its per-subtype routes belong in the discriminator base's file).

This is pre-existing — it predates #248 and #248 introduced no regression (it only added the hasAnyRdbSource(e) conjunct to the hono filter, deliberately leaving TPH handling untouched). Small fix: add the !isTphSubtype(e) conjunct to the hono filter, mirroring routes-file.ts. Ref: §9e.

[dmealing]

Closing — not tracking as a separate issue. This deferred item remains documented in the #248 design spec (docs/superpowers/specs/2026-08-01-issue-248-persistability-from-source-design.md §9) on main.