fix(web): preserve structured detail integrity

[outlier27-cell]

Problem

Closes #695. Web structured tool-detail projection silently dropped legitimate own __proto__ keys, changing the projection object's prototype. It also stopped at an exhausted node budget without reporting omitted array elements or later object properties.

Value

Operators receive intact structured evidence or an explicit truncation marker, rather than a complete-looking result that silently lost data.

Approach

Define own data properties without invoking prototype setters. Detect budget exhaustion before visiting a remaining item, preserving complete values exactly at the budget boundary. Existing policy still omits partial details and reports truncation.details. Reusable source findings are recorded in docs/research/WEB_STRUCTURED_DETAILS_2026-10-07.md.

Validation

• Special-key and array/object exhaustion regressions failed on the baseline, then passed after the fix; exact-boundary coverage prevents false omission claims.
• Node protocol suite: 25 passed.
• bun run check: passed.
• bun run test: executed; 2180 passed, 12 failed, 14 skipped in the local Windows Node suite. Existing renderer/footer assertions, symlink EPERM and worktree-validation timeout remain; runner stops before the UI suite. No full local pass is claimed. Exact-head GitHub CI will be verified.
• No installed browser, model or private Session was used.

Impact

Only Web evidence projection changes. No tools, model context, permissions, Session persistence or setup options change. Global prototype pollution is not claimed. Byte, depth, node, property and accessor boundaries remain bounded.

[outlier27-cell]

@tt-a1i 请审核此 PR。最新提交已通过完整 GitHub CI，当前可合并；如有需要调整的地方，我会在原分支及时修复。

[testikun]

已复查 结构化详情投影、特殊自有键和精确预算边界（提交 6726241cbe67），并核对相关调用点和回归覆盖。本次未发现新增的 P1/P2。