hosting: panel.t27 names its events EVENT_ (Darwin has EV_RECEIPT) and says whether the key file is private #8988

Problem

The trios app imports specs/hosting/panel.t27 (#8975, merged in #8977) through t27c gen-c and a Clang module (gHashTag/trios#1756). Building the app against it found three things the card should hold and does not:

• EV_* collides with Darwin: <sys/event.h> defines EV_RECEIPT, and every Swift file that imports the card also imports Darwin, so EV_RECEIPT is ambiguous and the app does not compile.
• The app shows whether the host key file is private. The rule (no group or other bit, toolchain.t27 GROUP_OTHER_BITS) and the key file's place (AGENT_DIR, KEY_FILE) are toolchain.t27's; the card does not expose them, so Swift would have to restate them.

Scope

• Rename the card's events EV_* to EVENT_*.
• Add key_file_private(mode) on toolchain.t27 GROUP_OTHER_BITS, and import AGENT_DIR and KEY_FILE, with a test.

Acceptance

• t27c test-report specs/hosting/panel.t27: every test passes, none vacuous; the pinned t27b passes them.
• A negative control (key_file_private returns true) fails the_key_file_is_the_owners_alone.
• Seal re-saved.

Boundary

• specs/hosting/panel.t27
• .trinity/seals/hosting_HostingPanel.json

🤖 Generated with Claude Code

User Scenarios

• Given the panel.t27 card defines events with EV_* prefix, when a Swift file imports the generated card and also imports Darwin's <sys/event.h>, then EV_RECEIPT is ambiguous and compilation fails.
• Given the panel.t27 card does not expose key_file_private, AGENT_DIR, or KEY_FILE, when Swift code needs to check whether the host key file is private, then it must restate the rule and paths from toolchain.t27.
• Given the panel.t27 card renames its events to EVENT_* and adds key_file_private(mode) importing AGENT_DIR, KEY_FILE, and GROUP_OTHER_BITS from toolchain.t27, when the test suite runs, then all tests pass and the negative control correctly fails.

Requirements

• FR-001: The panel.t27 card MUST rename all EV_* event constants to EVENT_* to avoid collision with Darwin's EV_RECEIPT.
• FR-002: The panel.t27 card MUST import AGENT_DIR, KEY_FILE, and GROUP_OTHER_BITS from toolchain.t27.
• FR-003: The panel.t27 card MUST define a key_file_private(mode) function that returns true when the file mode has no group or other bits set (using GROUP_OTHER_BITS).
• FR-004: The panel.t27 card MUST include a test for key_file_private that passes for a private key file and a negative control that fails when the function incorrectly returns true.