[caulif]

Fixes #1169

Problem

Chat could fail to open a file the assistant had just written. For example, C:\demo project\readme.md could be left as plain inline code or scanned as only its trailing segment, while clicking the Write tool path could report no match. Spaces in POSIX paths, Windows drive letters and backslashes, UNC paths, and multi-dot filenames exposed related parsing failures. A same-named file elsewhere could also make an incorrect fallback look plausible.

Changes

• Keep complete file references through chat prose, inline code, Markdown links, and tool rows, including spaced absolute paths, Windows and UNC syntax, Unicode names, and multi-dot filenames. Preserve separate links when prose contains multiple paths.
• Send absolute references to the existing main-process resolver intact. Resolve an absolute path only to that exact file within an allowed project, session scratch, or attachment root; distinguish an outside-root path from a missing in-root file in the UI.
• Validate real paths and regular-file status before returning relative, attachment-blob, or indexed fuzzy matches. Escaping or dangling links cannot redirect an exact reference to a same-named file; fuzzy matching retains the existing root and suffix priority while skipping stale or escaping entries. The downstream open operation still performs its own access check.
• Update the IPC contract, localized messages, specifications, E2E scenario, and regression tests.

Unmarked relative paths whose first segment contains spaces remain plain text because they cannot be reliably distinguished from ordinary prose. An explicit @"my project/page.md" reference remains available. Home paths remain plain text.

Validation

• Synced with upstream main at 110fc6675; pnpm check:pr-base and git diff --check upstream/main...HEAD passed.
• Windows: 104 relevant desktop tests passed, 0 skipped. The attachment-root junction escape assertion runs without file-symlink privileges.
• Ubuntu WSL: 29 file-resolution tests passed, 0 skipped, including a real attachment-blob file-symlink escape assertion. The Windows junction test and POSIX file-symlink test exercise different link types.
• Workspace dependency build, desktop typecheck, Electron/Vite build, lint, and docs checks passed.
• The reporter manually checked Windows chat-click scenarios on an earlier packaged candidate and reported success. The candidate after this upstream sync has not received another manual UI pass.

Remaining verification

pnpm test:e2e:transcript did not produce a UI verdict: Electron's renderer returned no probe result (exit=null). This is not counted as a passing E2E test. Actual macOS/Linux UI clicks have not been tested; the WSL result above is a resolver test.