feat(nvim): view blocked tool calls via :LucidBlocks

[alexander-blackwell]

Closes #320.

What

The GUI Security panel's blocked-tool-call list, now in the terminal and Neovim (increment P-NVIM.7). A read-only lucid blocks CLI plus :LucidBlocks / <leader>lb show the tool calls the security gate quarantined.

Why

lucid tui, bare lucid, and lucid acp run the same fail-closed gate + scanner as the desktop GUI, but a terminal/Neovim user had no way to SEE what the gate blocked. The GUI reads quarantines from agent_obs.duckdb, which a live bare-lucid session holds read-write, so a cross-process READ_ONLY open fails: a pure terminal session's blocks were invisible.

How

• tools/blocks_cli.ts: read-only lucid blocks [--all] [--json], merging the lock-free JSONL block log with the DuckDB quarantines (securitySnapshot, opened READ_ONLY, skipped when the DB is held). Pure read: no agent, no gate spawn, no mutation.
• harness/omp/block_log.ts: a scanner-free block mirror. The in-process gate appends each block to ~/.omp/lucid-blocks.jsonl when the launcher opts in via LUCID_BLOCK_LOG, so a block is visible DURING a live session. Env-gated and fail-safe, invoked AFTER the block decision: it can never perturb the fail-closed gate. The GUI never sets the env, so it never double-writes.
• harness/launcher/lucid_acp.ts: route lucid blocks; point the gated spawn env at the block log (bare-lucid only, since the GUI spawns omp directly).
• extensions/neovim/lua/lucid/init.lua + plugin/lucid.lua: M.blocks() read-only float + :LucidBlocks + <leader>lb.
• docs/NEOVIM.md: documented.

Invariants

• The fail-closed gate is untouched: the mirror is best-effort, env-gated, and runs after the block decision. make test-failclosed 15/15.
• Metadata only: the mirror records tool, a severity summary, and the reason, never raw scanned content.

Testing

• harness/omp/block_log.test.ts (9): buildBlockRecord severity/findings/fail-closed cases; mirrorBlock env-gate, JSONL append with recursive mkdir, swallowed write failure.
• tools/blocks_cli.test.ts (8): readBlockLog parsing + approve/dismiss marker replay + defaults; blockList/runBlocks (filtered to source === "log" so the repo's real DuckDB rows never flake them).
• lucid_acp.test.ts: main blocks --json routing (never falls through to the TUI/ACP).
• _blocks_lines headless assertions in helpers_spec.lua (luac -p clean; run by CI where nvim exists).
• make demo-P-NVIM.7 green; make test 2331 pass / 0 fail + sidecar green; root tsc + license headers clean.

Note

Stacked on feat/nvim-knowledge-graph (#316). The base auto-retargets to master when #316 merges; review this diff after #316.