fix(lint): use parsed declarations in formatting guard

[vicmcorrea]

Problem and fix

Bend accepts indented top-level declarations, but bundled bend-lint misses their names when rebuilding the declaration-comparison seed. Even comparing the original source with itself fails, so --fix refuses safe formatting of valid indented definitions, types, laws, and proofs.

Record the root parser's declaration keys through the existing in-memory seam and use them to rebuild the seed. Comparison-only parsing suspends and restores the observer, including on parse failures, so overlapping rules cannot overwrite another check's declarations. This adapts the parser-derived formatter guard from MattCozendey's standalone bend-lint change.

Blast radius

• tools/bend-lint/src/seam.ts: observes parser declaration keys during lint checks and changes the seed used by sameDeclarations. This affects rules using that comparison, including the format/layout safe-fix guard. Snapshot comparisons restore the active observer on success and failure.
• tools/bend-lint/rules/format.test.ts: adds regression coverage for indented declarations, semantic changes, multiline literals, and overlapping rules.

Only these two bundled-tool files change. The formatter layout engine, language/compiler sources, generated-program runtimes, and gates are unchanged. Tests remain in bend-lint's own suite, following the maintainer guidance in #1389.

Regression evidence

• The three new declaration regressions fail against the original seam. They cover spaces/tabs, LF/CRLF, definitions, types, local/imported proofs, and unsafe declarations. Controls reject changed values, added/removed declarations, and changed literal contents.
• Removing only observer suspension makes the overlapping-rule regression fail. The corrected implementation also handles malformed comparison input without contaminating another check.
• Real CLI checks reproduce main's refusal and verify the safe fix on this branch. Execution remains 7, and a second lint run is clean.

Checks

• bend-lint suite: 126 passed, 0 failed; 827 assertions.
• Local repository gate: 54/54, using CI-pinned ttok 0.3.
• GitHub repo-gate: passed on c9b3283.
• git diff --check: passed.

Validation limits

Typecheck is not clean on main or this branch: both report the same two pre-existing TS2339 errors in protected bend2/bend.ts at lines 2040 and 3771. No new typecheck diagnostics were introduced.

Local tests ran on macOS arm64 with Bun 1.3.11. Windows and the cluster gates were not run. The additional in-memory parser hook depends on the current parse_book signature and declaration ordering; signature, startup, and patch-drift checks cover that dependency.