fix: preserve format assertion policy in remote schemas

[fitchmultz]

Problem

formatAssertion: false is respected by a directly compiled schema but lost when addRemoteSchema selects the remote document's draft keywords. A registered email schema therefore rejects a non-email string even though its registering owner requested annotation-only formats.

Correction

• Retain the effective format policy in the compiled context after meta-schema policy evaluation.
• Apply that policy when registering remote schemas, including transitive registration.
• Disable only the format instance validator on remotes; preserve the format parser and malformed-schema diagnostics.

Default and explicit-true behavior remain unchanged. Newly registered schemas follow their registering owner; already compiled external schemas retain their original policy. No resolver, dialect-selection, dependency, or generated distribution changes are included.

Related work

This addresses remote registration separately from #125 / #121, which correct local schema parsing when assertions are disabled. Thanks to @cpruijsen for the related addValidate approach in #125; this PR uses that hook on the remote path to preserve its existing parser. It leaves the local filter unchanged and neither supersedes nor closes #125. When composing the two, retain this context-policy assignment before #125's local keyword mapping.

Verification

• 69 regression cases across drafts 04, 06, 07, 2019-09 and 2020-12: direct/registered schemas, retrieval identifiers, anchors, transitive registration, owner-policy changes, effective meta-schema policy, and malformed remote formats. Against unchanged production code, 18 annotation-mode cases fail and 51 pass; all 69 pass with this correction.
• Full unit/in-process Bowtie suite: 1,091 passing, 3 existing pending. Full specification suite: 7,513 passing, 9 existing pending.
• Source and built CJS/ESM controls: 30 groups / 120 value checks per format; additional in-process Bowtie controls: 25 groups / 100 values.
• Normal ESM, CJS, IIFE and declaration builds pass; integrated attw reports no problems. Changed-file lint and whitespace checks pass.
• Full type/lint checks retain the measured clean-main baseline: 4 source-type diagnostics, 107 test-type diagnostics, and 3 unused-import lint errors. Those checks are not reported green.

Based on main 65578c185fc324ebf8fcc8f6e654e85cbfab4da8, with pnpm 10.34.5. Source/tests only. No network validation, external Docker Bowtie, load test, or release was performed.