merge: AgentProject membership — the junction is now load-bearing

Merges feat/agent-project-membership (task 166/152). An agent can finally join
many projects: membership routes, per-membership role and optional brain
override, chat resolving context from the membership, and CLI attach-agent /
detach-agent / get memberships. The legacy Agent.projectId fallback is kept for
this release as the schema comment promises.

Conflict resolved in main.ts: that branch added its RBAC case to
mapUrlToPermission inline, while this branch had extracted the function to
middleware/url-permission.ts so it could be tested. Kept the extraction and
ported the case into it — joining a team is `edit:agents:<name>`, not
`create:agents`, which is the authority to mint a whole agent.

Also fixes something the extraction makes possible. security.test.ts contained a
hand-copied reproduction of mapUrlToPermission, because main.ts self-invokes
main() and nothing in it was importable. A security test asserting against a
copy stops testing the system the moment the real one changes, and this copy had
already drifted. It now imports the real function; all 18 assertions still pass,
against the code that actually runs.

Local: build clean, workspace 2550 passed, lint unchanged at 794 errors.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4wNHWf7xSwnZCWpJcyv9p

.taskmaster/tasks/task_070.md

@@ -0,0 +1,37 @@
+# Task ID: 70
+
+**Title:** Add shell completions for new CLI flags
+
+**Status:** done
+
+**Dependencies:** 59 ✓, 60 ✓
+
+**Priority:** low
+
+**Description:** Update shell completion scripts (bash, zsh, fish) to include completions for new flags: --priority, --link, -A, and gated values.
+
+**Details:**
+
+1. Update `/completions/mcpctl.fish`:
+   ```fish
+   # create prompt completions
+   complete -c mcpctl -n '__fish_seen_subcommand_from create; and __fish_seen_subcommand_from prompt' -l priority -d 'Priority level (1-10)' -a '(seq 1 10)'
+   complete -c mcpctl -n '__fish_seen_subcommand_from create; and __fish_seen_subcommand_from prompt' -l link -d 'Link to MCP resource (project/server:uri)'
+   
+   # get prompt completions  
+   complete -c mcpctl -n '__fish_seen_subcommand_from get; and __fish_seen_subcommand_from prompt' -s A -l all-projects -d 'Show prompts from all projects'
+   ```
+
+2. Update bash completions similarly
+
+3. Update zsh completions similarly
+
+4. Add dynamic completion for priority values (1-10)
+
+**Test Strategy:**
+
+- Manual test: Fish completions suggest --priority with values 1-10
+- Manual test: Fish completions suggest --link flag
+- Manual test: Fish completions suggest -A/--all-projects
+- Manual test: Bash completions work similarly
+- Manual test: Zsh completions work similarly