refactor: sweep technical debt

[hakula139]

Summary

Sweeps the repo after the broad review pass, removing stale compatibility debt and tightening several correctness boundaries in sessions, slash commands, config loading, file mutation, and tool output capture.

This PR also refreshes the Markdown docs against the current implementation and external reference notes so repository guidance matches the code that now ships.

Design decisions

• Treat the session schema as early-stage owned data. The loader now rejects unknown entry variants instead of carrying compatibility shims for legacy JSONL shapes that are safe to discard.
• Keep credential-bearing config user-scoped. Project config can no longer redirect API credentials through api_key or base_url, and invalid token-budget env input fails loudly instead of silently changing behavior.
• Make the file tracker the content gate. Read, Edit, Write, and resume now share one content-hash validation path, including regular-file and size checks before reading or mutating tracked files.
• Scope compact replay sidecars to accepted tail messages. Resume loading filters tool metadata and file snapshots with the same compact-tail boundary as messages, preventing stale sidecars from leaking across compaction.
• Bound process output and pipe lifetime together. Bash tool execution drains stdout / stderr concurrently under the command deadline while retaining only capped buffers.
• Keep command surfaces bounded. /resume now shares the CLI session-list cap, and /diff truncation hints match whether the repository has a HEAD commit.

Changes

File	Description
session/entry.rs, session/store.rs, session/sanitize.rs, agent/compaction.rs, tui/components/chat.rs	Remove schema compatibility shims, make compact replay sidecar filtering boundary-aware, and preserve real prompts when stripping synthetic compact prefixes from resumed chat history.
config.rs, config/file.rs, docs/guide/configuration.md	Reject project-level credential redirects, validate Anthropic max-token env input, and document the user-config-only client settings.
file_tracker.rs, tool/read.rs, tool/edit.rs, tool/write.rs, session/handle.rs, docs/design/session/file-tracking.md	Centralize tracked-file validation, verify current bytes before mutations and snapshot restore, drop oversized or non-regular tracked files before reading, and document the stronger invariant.
tool/bash.rs, docs/design/tools/truncation.md	Enforce the command timeout across child wait and pipe collection while keeping stdout / stderr capture bounded.
slash/diff.rs, slash/resume.rs, slash/confirm.rs, tui/app.rs, slash/model.rs, slash/effort.rs	Fix no-HEAD diff coverage, cap /resume list loading, gate config-changing pickers while busy, ignore modified confirm-delete keys, and roll back theme previews when forced modals close.
tui/components/chat/blocks/tool/glob.rs, tui/components/chat/blocks/error.rs	Share truncation-footer parsing for glob titles and keep error-marker helpers test-only.
README.md, CLAUDE.md, docs/**/*	Sync command docs, CI guidance, research notes, and design descriptions with current behavior and verified external reference state.

Test plan

• cargo fmt --all --check
• cargo build
• cargo clippy --all-targets -- -D warnings: zero warnings
• cargo test: 1954 tests pass
• cargo llvm-cov --ignore-filename-regex 'main\.rs': 98.94% line coverage
• pnpm lint
• pnpm spellcheck

[codecov]

Codecov Report

❌ Patch coverage is 98.20359% with 18 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/oxide-code/src/tool/bash.rs	93.93%	10 Missing ⚠️
crates/oxide-code/src/file_tracker.rs	96.78%	7 Missing ⚠️
crates/oxide-code/src/config/file.rs	98.38%	1 Missing ⚠️

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