tip: limit persisted snapshot diff patches (#50385)

[kvnloo]

Tip leaf (fork-only) — CLEAN

Maps to work-order issue #152. Upstream origin anomalyco#50385 (not touched / not promoted).

What: Cap per-file and total patch text in diffFull so huge tracked/generated files do not bloat message rows; restore still uses snapshot hashes.

Commit: d8f564733f059cd6781860516b104d679f1ee655
Origin tip SHA: d12ea126e584

Proof: fail→pass on tip tests diffFull omits patch text... + diffFull limits total... (GREEN 2 / NEG 2 fail / RESTORE 2).

github_writes_origin: 0. Codex promote parked.

[github-actions]

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[github-actions]

Hey! Your PR title tip: limit persisted snapshot diff patches (#50385) doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[kvnloo]

READY_UPSTREAM

Rechecked before promotion:

• upstream PR fix(snapshot): limit persisted diff patches anomalyco/opencode#50385 is still open
• upstream head is exactly d12ea126e584ae5ab072d190ef1ce19cdcaa2981
• no prior kvnloo validation comment is present
• this fork leaf's fail → pass → restore evidence therefore still applies to the exact upstream head

GitHub App cannot write to anomalyco/opencode from this environment (403). Hermes/local-gh may post the evidence comment from this fork PR. Do not open a duplicate PR.