fix: honest Blueprint-gated states, enforced pause, real A9 storage prices

[Gift-Stack]

Closes out the remaining honesty gaps: every feature that needs the (not-yet-built) Blueprint project pipeline now says so explicitly, and no handler fabricates data. Four atomic commits.

Bridge

• workspace.open no longer ignores its path. Demo/example paths map to their own sandbox workspaces; any other path fails honestly: "Opening a Blueprint project from disk is not supported by this bridge build yet…". Previously a dead ternary silently returned the demo workspace as if it were your project.
• account.revealMnemonic no longer fabricates a 24-word phrase. Sandbox treasuries are seed-derived; it now throws "…have no mnemonic to reveal."
• contract.abi returns available: false + a note ("needs an open Blueprint project (.abi.json)…") instead of a bare empty list; mocks in lockstep with available: true.
• test.subscribe emits a run-end with an unavailable payload instead of a fake test failure.
• time.setPaused is now enforced. Paused pins blockchain.now; running time flows as wall clock + offset (re-pinned before every execution path); advance/setNow while paused move the frozen point; unpause resumes forward with no backwards jump.
• Socket close no longer leaks subscriptions (dead sub ids are removed from every workspace).

App

• A1 open-project dialog surfaces the bridge error inline (was swallowed).
• A2 reveal-mnemonic renders the honest state; the mainnet warning only shows next to an actual phrase.
• A3 ABI section explains the degraded state; A20 shows a "No test project attached" EmptyState instead of a red failed run (real failures still render as failures).
• A9 projects storage fees from real config p18 prices ((cells·cell_price_ps + bits·bit_price_ps)·seconds / 2^16, bigint) over a clearly-labeled reference footprint — replacing the invented 10 nanoTON/s constant. Honest "prices unavailable" note when p18 isn't decoded.
• Removed the stale RATIFY_IN_A6_SPIKE list (field names long since ratified against the live bridge).

Verification

• pnpm tsc + pnpm lint green; bridge smoke ALL OK.
• Live checks: fake path → honest error; demo/example paths open; mnemonic → honest error; pause froze now across 1.6s, +3600 advance moved it exactly, unpause resumed flowing; contract.abi returns the degraded shape.