feat(context): unify declarative context reload

[limityan]

Problem

Declarative context can change while a BitFun session remains open, but users currently have separate or incomplete refresh paths. Skills can be refreshed independently, while workspace instructions may remain cached until a later lifecycle event. Shared TUI also needs the same behavior without creating a second runtime owner.

What changed

• Adds one user-facing command: /reload [skills|instructions].
  • /reload refreshes the existing Skill Registry and invalidates the current Session instruction cache.
  • /reload skills and /reload instructions target one existing owner.
  • /reload-skills remains a hidden input compatibility alias only.
• Supports local Desktop, Embedded CLI, and Shared TUI through one typed Core coordination entry point.
• Keeps Browser, Dispatch, ACP, and unsupported/remote surfaces fail-closed with a clear local-only message.
• Resolves runtime-free workspace instructions from existing local or remote workspace services:
  • AGENTS.override.md / AGENTS.md
  • Claude root/local files, unconditional rules, and bounded local imports
  • OpenCode project-local JSON/JSONC instruction entries with exact paths or globs
• Reuses one JSONC parser across OpenCode agent, command, MCP, and instruction sources.
• Advances the private Shared TUI IPC protocol to v6 for the combined Session rename and context reload wire.

Behavioral boundary

• Reload never rewrites the active turn; changes apply to the next message.
• A cache generation guard prevents an active turn from repopulating invalidated instructions.
• No watcher, startup re-import, current-turn hot replacement, URL imports, path-scoped Claude rules, source graph, hooks, MCP/model/theme reload, or Plugin Runtime work is included.
• Skill Registry, Session context, workspace I/O, and ecosystem parsing retain their existing owners; Core only coordinates them.

Safety and performance

• Instruction discovery has bounded probes, file count, import depth, per-file size, and aggregate content limits.
• Exact no-follow metadata checks reject symlinks and non-regular files before reads.
• Remote SFTP caches are connection-generation scoped so stale sessions cannot publish into or invalidate a reconnected host.
• Container and raw SFTP directory reads stop at the configured producer-side limit.
• Missing files are treated as absent; permission, transport, and transient inspection failures remain visible and are not cached as empty context.

Validation

• cargo check --workspace
• cargo check -p bitfun-services-integrations --features remote-ssh-concrete
• cargo test -p bitfun-agent-runtime-ipc (37 passed)
• cargo test -p bitfun-cli --no-run
• cargo test -p bitfun-cli --test product_assembly_cli (11 passed)
• node --test scripts/check-core-boundaries.test.mjs (16 passed)
• focused CLI Shared rename/help/status tests
• focused remote SSH manager tests (21 passed, 1 ignored) and remote filesystem tests (3 passed)
• Web type-check and reload command/API tests (64 passed)
• i18n audit, repository hygiene, GitHub config checks, and git diff --check

Independent adversarial reviews found and verified fixes for unsupported-surface routing, no-follow/bounded remote reads, cache races, SFTP generation isolation, the rebased IPC version collision, Shared TUI capability copy, and CLI deployment adapter isolation. The final review reported no remaining P0-P2 findings.